Handle install vs build include directories

Fix target_include_directories to appropriately handle build-tree and the install-tree.
diff --git a/OGLCompilersDLL/CMakeLists.txt b/OGLCompilersDLL/CMakeLists.txt
index d257828..af4ab58 100644
--- a/OGLCompilersDLL/CMakeLists.txt
+++ b/OGLCompilersDLL/CMakeLists.txt
@@ -11,5 +11,5 @@
 if(ENABLE_GLSLANG_INSTALL)
     install(TARGETS OGLCompiler EXPORT OGLCompilerTargets
             ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
-	install(EXPORT OGLCompilerTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT OGLCompilerTargets DESTINATION lib/cmake)
 endif(ENABLE_GLSLANG_INSTALL)
diff --git a/SPIRV/CMakeLists.txt b/SPIRV/CMakeLists.txt
index 3ddf6f1..94db899 100644
--- a/SPIRV/CMakeLists.txt
+++ b/SPIRV/CMakeLists.txt
@@ -46,7 +46,9 @@
 add_library(SPIRV ${LIB_TYPE} ${SOURCES} ${HEADERS})
 set_property(TARGET SPIRV PROPERTY FOLDER glslang)
 set_property(TARGET SPIRV PROPERTY POSITION_INDEPENDENT_CODE ON)
-target_include_directories(SPIRV PUBLIC ..)
+target_include_directories(SPIRV PUBLIC 
+	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/..>
+	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
 if (ENABLE_SPVREMAPPER)
     add_library(SPVRemapper ${LIB_TYPE} ${SPVREMAP_SOURCES} ${SPVREMAP_HEADERS})
@@ -67,7 +69,9 @@
         PRIVATE ${spirv-tools_SOURCE_DIR}/source
     )
     target_link_libraries(SPIRV glslang SPIRV-Tools-opt)
-    target_include_directories(SPIRV PUBLIC ../External)
+    target_include_directories(SPIRV PUBLIC
+		$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../External>
+		$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/External>)
 else()
     target_link_libraries(SPIRV glslang)
 endif(ENABLE_OPT)
@@ -97,8 +101,8 @@
                 ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
     endif()
 	
-	install(EXPORT SPVRemapperTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
-	install(EXPORT SPIRVTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT SPVRemapperTargets DESTINATION lib/cmake)
+	install(EXPORT SPIRVTargets DESTINATION lib/cmake)
 
     install(FILES ${HEADERS} ${SPVREMAP_HEADERS} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/SPIRV/)
 endif(ENABLE_GLSLANG_INSTALL)
diff --git a/StandAlone/CMakeLists.txt b/StandAlone/CMakeLists.txt
index 03d6401..89e91c0 100644
--- a/StandAlone/CMakeLists.txt
+++ b/StandAlone/CMakeLists.txt
@@ -33,7 +33,9 @@
 
 target_link_libraries(glslangValidator ${LIBRARIES})
 target_link_libraries(spirv-remap ${LIBRARIES})
-target_include_directories(glslangValidator PUBLIC ../External)
+target_include_directories(glslangValidator PUBLIC 
+	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../External>
+	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/External>)
 
 if(WIN32)
     source_group("Source" FILES ${SOURCES})
@@ -46,12 +48,12 @@
     install(TARGETS spirv-remap EXPORT spirv-remapTargets
             RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 	
-	install(EXPORT glslangValidatorTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
-	install(EXPORT spirv-remapTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT glslangValidatorTargets DESTINATION lib/cmake)
+	install(EXPORT spirv-remapTargets DESTINATION lib/cmake)
             
     if(BUILD_SHARED_LIBS)
         install(TARGETS glslang-default-resource-limits EXPORT glslang-default-resource-limitsTargets
                 LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
-		install(EXPORT glslang-default-resource-limitsTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+		install(EXPORT glslang-default-resource-limitsTargets DESTINATION lib/cmake)
     endif()
 endif(ENABLE_GLSLANG_INSTALL)
diff --git a/glslang/CMakeLists.txt b/glslang/CMakeLists.txt
index 9019d81..9507ef0 100644
--- a/glslang/CMakeLists.txt
+++ b/glslang/CMakeLists.txt
@@ -86,7 +86,9 @@
 set_property(TARGET glslang PROPERTY FOLDER glslang)
 set_property(TARGET glslang PROPERTY POSITION_INDEPENDENT_CODE ON)
 target_link_libraries(glslang OGLCompiler OSDependent)
-target_include_directories(glslang PUBLIC ..)
+target_include_directories(glslang PUBLIC 
+	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/..>
+	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
 if(WIN32 AND BUILD_SHARED_LIBS)
     set_target_properties(glslang PROPERTIES PREFIX "")
@@ -114,7 +116,7 @@
         install(TARGETS glslang EXPORT glslangTargets
                 ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
     endif()
-	install(EXPORT glslangTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT glslangTargets DESTINATION lib/cmake)
 endif(ENABLE_GLSLANG_INSTALL)
 
 if(ENABLE_GLSLANG_INSTALL)
diff --git a/glslang/OSDependent/Unix/CMakeLists.txt b/glslang/OSDependent/Unix/CMakeLists.txt
index 4a434ef..91fb45a 100644
--- a/glslang/OSDependent/Unix/CMakeLists.txt
+++ b/glslang/OSDependent/Unix/CMakeLists.txt
@@ -22,5 +22,5 @@
 if(ENABLE_GLSLANG_INSTALL)
     install(TARGETS OSDependent EXPORT OSDependentTargets
             ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
-	install(EXPORT OSDependentTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT OSDependentTargets DESTINATION lib/cmake)
 endif(ENABLE_GLSLANG_INSTALL)
diff --git a/glslang/OSDependent/Windows/CMakeLists.txt b/glslang/OSDependent/Windows/CMakeLists.txt
index 321fd4f..f6bd4e9 100644
--- a/glslang/OSDependent/Windows/CMakeLists.txt
+++ b/glslang/OSDependent/Windows/CMakeLists.txt
@@ -17,5 +17,5 @@
 if(ENABLE_GLSLANG_INSTALL)
     install(TARGETS OSDependent EXPORT OSDependentTargets
             ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
-	install(EXPORT OSDependentTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT OSDependentTargets DESTINATION lib/cmake)
 endif(ENABLE_GLSLANG_INSTALL)
diff --git a/gtests/CMakeLists.txt b/gtests/CMakeLists.txt
index 6e57443..77d217f 100644
--- a/gtests/CMakeLists.txt
+++ b/gtests/CMakeLists.txt
@@ -33,7 +33,7 @@
         if(ENABLE_GLSLANG_INSTALL)
             install(TARGETS glslangtests EXPORT glslangtestsTargets
                     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
-			install(EXPORT glslangtestsTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+			install(EXPORT glslangtestsTargets DESTINATION lib/cmake)
         endif(ENABLE_GLSLANG_INSTALL)
 
         set(GLSLANG_TEST_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../Test")
diff --git a/hlsl/CMakeLists.txt b/hlsl/CMakeLists.txt
index 70cd28e..44f9d6a 100644
--- a/hlsl/CMakeLists.txt
+++ b/hlsl/CMakeLists.txt
@@ -41,5 +41,5 @@
         install(TARGETS HLSL EXPORT HLSLTargets
                 ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
     endif()
-	install(EXPORT HLSLTargets DESTINATION ${LIB_INSTALL_DIR}/cmake)
+	install(EXPORT HLSLTargets DESTINATION lib/cmake)
 endif(ENABLE_GLSLANG_INSTALL)