Simplify flag specification with MVSC

Addresses many linking errors for the `castxml` binary.

Author: thewtex

CMakeLists.txt

@@ -12,19 +12,6 @@ enable_language(C)
 enable_language(CXX)
 
 
-# Use a static runtime with MSVC
-if(MSVC)
-  foreach(flag
-    CMAKE_CXX_FLAGS
-    CMAKE_CXX_FLAGS_RELEASE
-    CMAKE_C_FLAGS
-    CMAKE_C_FLAGS_RELEASE
-    )
-    if(${flag} MATCHES "/MD")
-      string(REGEX REPLACE "/MD" "/MT" ${flag} "${${flag}}")
-    endif()
-  endforeach()
-endif()
 set(CMAKE_CXX_STANDARD "17")
 
 
@@ -81,14 +68,10 @@ else()
     CMAKE_GENERATOR "${CMAKE_GENERATOR}"
     CMAKE_CACHE_ARGS
       -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
-      "-DCMAKE_CXX_FLAGS:STRING=${CMAKE_CXX_FLAGS} -w"
-      "-DCMAKE_CXX_FLAGS_RELEASE:STRING=${CMAKE_CXX_FLAGS_RELEASE}"
       -DCMAKE_CXX_STANDARD:STRING=${CMAKE_CXX_STANDARD}
       -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
-      "-DCMAKE_C_FLAGS:STRING=${CMAKE_C_FLAGS} -w"
-      "-DCMAKE_C_FLAGS_RELEASE:STRING=${CMAKE_C_FLAGS_RELEASE}"
+      -DLLVM_STATIC_LINK_CXX_STDLIB:BOOL=ON
       -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
-      -DLLVM_USE_CRT_RELEASE:STRING=MT
       -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
       -DLLVM_INSTALL_PREFIX:PATH=<INSTALL_DIR>
       -DLLVM_ENABLE_TERMINFO:BOOL=OFF
@@ -114,12 +97,8 @@ else()
     CMAKE_GENERATOR "${CMAKE_GENERATOR}"
     CMAKE_CACHE_ARGS
       -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
-      "-DCMAKE_CXX_FLAGS:STRING=${CMAKE_CXX_FLAGS} -w"
-      "-DCMAKE_CXX_FLAGS_RELEASE:STRING=${CMAKE_CXX_FLAGS_RELEASE}"
       -DCMAKE_CXX_STANDARD:STRING=${CMAKE_CXX_STANDARD}
       -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
-      "-DCMAKE_C_FLAGS:STRING=${CMAKE_C_FLAGS} -w"
-      "-DCMAKE_C_FLAGS_RELEASE:STRING=${CMAKE_C_FLAGS_RELEASE}"
       -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
       -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
       -DCLANG_INCLUDE_DOCS:BOOL=OFF
@@ -141,7 +120,7 @@ endif()
 
 # Use a static C++ library on GCC/Linux
 if(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_SYSTEM_NAME MATCHES "Linux")
-  set(extra_flags "-static-libstdc++")
+  set(linux_args "-DCMAKE_CXX_FLAGS:STRING=-static-libstdc++")
 endif()
 # 2024-04-12 master
 set(CastXML_GIT_TAG v0.6.5 CACHE STRING "CastXML Git revision.")
@@ -153,16 +132,13 @@ ExternalProject_Add(castxml
   CMAKE_GENERATOR "${CMAKE_GENERATOR}"
   CMAKE_CACHE_ARGS
     -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
-    "-DCMAKE_CXX_FLAGS:STRING=${CMAKE_CXX_FLAGS} -w ${extra_flags}"
-    "-DCMAKE_CXX_FLAGS_RELEASE:STRING=${CMAKE_CXX_FLAGS_RELEASE}"
     -DCMAKE_CXX_STANDARD:STRING=${CMAKE_CXX_STANDARD}
     -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
-    "-DCMAKE_C_FLAGS:STRING=${CMAKE_C_FLAGS} -w"
-    "-DCMAKE_C_FLAGS_RELEASE:STRING=${CMAKE_C_FLAGS_RELEASE}"
     -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
     -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
     -DLLVM_DIR:PATH=${LLVM_DIR}
     ${osx_args}
+    ${linux_args}
   ${verbose_command}
   LOG_BUILD 0
   INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}/castxml