[cmake] Fix clang-cl cross-compilation on macOS
macOS paths usually start with /Users, which clang-cl interprets as a
macro undefine, leading to pretty much everything failing to compile.
CMake should be taught to put a -- in its compilation rules for clang-cl
(and I've been meaning to submit that upstream for a while). In the
meantime, however, and to support older CMake versions, we can just
create a custom make rules override to fix the compilation rules.
Differential Revision: https://reviews.llvm.org/D41219
llvm-svn: 320785
diff --git a/llvm/cmake/platforms/ClangClCMakeCompileRules.cmake b/llvm/cmake/platforms/ClangClCMakeCompileRules.cmake
new file mode 100644
index 0000000..a3bcf1c
--- /dev/null
+++ b/llvm/cmake/platforms/ClangClCMakeCompileRules.cmake
@@ -0,0 +1,9 @@
+# macOS paths usually start with /Users/*. Unfortunately, clang-cl interprets
+# paths starting with /U as macro undefines, so we need to put a -- before the
+# input file path to force it to be treated as a path. CMake's compilation rules
+# should be tweaked accordingly, but until that's done, and to support older
+# CMake versions, overriding compilation rules works well enough. This file will
+# be included by cmake after the default compilation rules have already been set
+# up, so we can just modify them instead of duplicating them entirely.
+string(REPLACE "-c <SOURCE>" "-c -- <SOURCE>" CMAKE_C_COMPILE_OBJECT "${CMAKE_C_COMPILE_OBJECT}")
+string(REPLACE "-c <SOURCE>" "-c -- <SOURCE>" CMAKE_CXX_COMPILE_OBJECT "${CMAKE_CXX_COMPILE_OBJECT}")