[cmake] [libcxxabi] Fix find_path() problems when cross compiling

When CMAKE_SYSROOT or CMAKE_FIND_ROOT_PATH is set, cmake
recommends setting CMAKE_FIND_ROOT_PATH_MODE_INCLUDE=ONLY
globally which means find_path() always prepends CMAKE_SYSROOT or
CMAKE_FIND_ROOT_PATH to all paths used in the search.

However, these find_path() invocations are looking for paths in
the libcxx and libunwind projects on the host system, not the
target system, which can be done by passing
NO_CMAKE_FIND_ROOT_PATH.

Differential Revision: https://reviews.llvm.org/D41623

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@323145 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dd43da2..35eb130 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -115,6 +115,7 @@
         ${CMAKE_BINARY_DIR}/${LIBCXXABI_LIBCXX_INCLUDES}
         ${LIBCXXABI_LIBCXX_INCLUDE_DIRS}
         ${LLVM_INCLUDE_DIR}/c++/v1
+  NO_CMAKE_FIND_ROOT_PATH
   )
 
 set(LIBCXXABI_LIBCXX_INCLUDES "${LIBCXXABI_LIBCXX_INCLUDES}" CACHE PATH
@@ -127,6 +128,7 @@
         ${LIBCXXABI_LIBCXX_INCLUDES}/../
         ${LIBCXXABI_LIBCXX_SRC_DIRS}
   NO_DEFAULT_PATH
+  NO_CMAKE_FIND_ROOT_PATH
   )
 
 if (LIBCXXABI_LIBCXX_PATH STREQUAL "LIBCXXABI_LIBCXX_PATH-NOTFOUND")
@@ -425,6 +427,7 @@
           ${LLVM_MAIN_SRC_DIR}/projects/libunwind/include
           ${LLVM_MAIN_SRC_DIR}/runtimes/libunwind/include
     NO_DEFAULT_PATH
+    NO_CMAKE_FIND_ROOT_PATH
   )
 
   if (LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL STREQUAL "LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL-NOTFOUND")