[cmake] Normalize TARGET_SUBDIR paths

Some code paths normalize ".." and thus don't create the directory.
But some execute in a shell thus requiring the directory to exist to be able to take the parent directory.
Normalize all the `TARGET_SUBDIR` variables to avoid this issue.

Author: tambry

libc/CMakeLists.txt

@@ -220,6 +220,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
   if(LIBC_LIBDIR_SUBDIR)
     string(APPEND LIBC_TARGET_SUBDIR /${LIBC_LIBDIR_SUBDIR})
   endif()
+  cmake_path(NORMAL_PATH LIBC_TARGET_SUBDIR)
 endif()
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND (LIBC_ENABLE_USE_BY_CLANG OR LIBC_TARGET_OS_IS_GPU))

libcxx/CMakeLists.txt

@@ -419,6 +419,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   if(LIBCXX_LIBDIR_SUBDIR)
     string(APPEND LIBCXX_TARGET_SUBDIR /${LIBCXX_LIBDIR_SUBDIR})
   endif()
+  cmake_path(NORMAL_PATH LIBCXX_TARGET_SUBDIR)
   set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LIBCXX_TARGET_SUBDIR})
   set(LIBCXX_GENERATED_INCLUDE_DIR "${LLVM_BINARY_DIR}/include/c++/v1")
   set(LIBCXX_GENERATED_MODULE_DIR "${LLVM_BINARY_DIR}/modules/c++/v1")

libcxxabi/CMakeLists.txt

@@ -187,6 +187,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   if(LIBCXXABI_LIBDIR_SUBDIR)
     string(APPEND LIBCXXABI_TARGET_SUBDIR /${LIBCXXABI_LIBDIR_SUBDIR})
   endif()
+  cmake_path(NORMAL_PATH LIBCXXABI_TARGET_SUBDIR)
   set(LIBCXXABI_HEADER_DIR ${LLVM_BINARY_DIR})
   set(LIBCXXABI_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LIBCXXABI_TARGET_SUBDIR})
   set(LIBCXXABI_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBCXXABI_TARGET_SUBDIR} CACHE STRING

libunwind/CMakeLists.txt

@@ -145,6 +145,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   if(LIBUNWIND_LIBDIR_SUBDIR)
     string(APPEND LIBUNWIND_TARGET_SUBDIR /${LIBUNWIND_LIBDIR_SUBDIR})
   endif()
+  cmake_path(NORMAL_PATH LIBUNWIND_TARGET_SUBDIR)
   set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LIBUNWIND_TARGET_SUBDIR})
   set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBUNWIND_TARGET_SUBDIR} CACHE STRING
       "Path where built libunwind libraries should be installed.")