Ensure definition of uppercase_CMAKE_BUILD_TYPE is available in HandleLLVMOptions.cmake module.

[EricWF]

Summary

HandleLLVMOptionsis used by libc++abi without including llvm/CMakeLists.txt when doing standalone builds. This means that uppercase_CMAKE_BUILD_TYPE is undefined. However uppercase_CMAKE_BUILD_TYPE is used in HandleLLVMOptions. This patch ensures that it is defined.

This might be a silly patch to ask for review on but I don't commit to LLVM often.

[EricWF]

This seems like a good candidate for post commit review.

cmake/modules/HandleLLVMOptions.cmake

 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 
+# uppercase_CMAKE_BUILD_TYPE is used in this module but is defined in
+# llvm/CMakeLists.txt. In order to allow for portible use of this module we
+# redefine it.
+string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+
 if(NOT LLVM_FORCE_USE_OLD_TOOLCHAIN)
   if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.7)