[NFC][CMake] quote ${CMAKE_SYSTEM_NAME} consistently (llvm#154537)

A CMake change included in CMake 4.0 makes `AIX` into a variable
(similar to `APPLE`, etc.)
https://gitlab.kitware.com/cmake/cmake/-/commit/ff03db6657c38c8cf992877ea66174c33d0bcb0b

However, `${CMAKE_SYSTEM_NAME}` unfortunately also expands exactly to
`AIX` and `if` auto-expands variable names in CMake. That means you get
a double expansion if you write:

`if (${CMAKE_SYSTEM_NAME}  MATCHES "AIX")`
which becomes:
`if (AIX  MATCHES "AIX")`
which is as if you wrote:
`if (ON MATCHES "AIX")`

You can prevent this by quoting the expansion of "${CMAKE_SYSTEM_NAME}",
due to policy
[CMP0054](https://cmake.org/cmake/help/latest/policy/CMP0054.html#policy:CMP0054)
which is on by default in 4.0+. Most of the LLVM CMake already does
this, but this PR fixes the remaining cases where we do not.

Author: daltenty

clang-tools-extra/clangd/CMakeLists.txt

@@ -6,7 +6,7 @@ add_subdirectory(support)
 
 # Configure the Features.inc file.
 if (NOT DEFINED CLANGD_BUILD_XPC)
-  if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+  if("${CMAKE_SYSTEM_NAME}" MATCHES "Darwin")
     set(CLANGD_BUILD_XPC_DEFAULT ON)
   else ()
     set(CLANGD_BUILD_XPC_DEFAULT OFF)
@@ -193,7 +193,7 @@ if(CLANGD_TIDY_CHECKS)
 endif()
 
 add_subdirectory(refactor/tweaks)
-if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+if ("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
   # FIXME: Make fuzzer not use linux-specific APIs, build it everywhere.
   add_subdirectory(fuzzer)
 endif()

clang/bindings/python/tests/CMakeLists.txt

@@ -35,7 +35,7 @@ if(WIN32)
 endif()
 
 # The Python FFI interface is broken on AIX: https://bugs.python.org/issue38628.
-if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   set(RUN_PYTHON_TESTS FALSE)
 endif()
 

clang/tools/libclang/CMakeLists.txt

@@ -93,7 +93,7 @@ if(MSVC)
   set(LLVM_EXPORTED_SYMBOL_FILE)
 endif()
 
-if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND NOT CYGWIN)
+if (UNIX AND NOT APPLE AND NOT "${CMAKE_SYSTEM_NAME}" MATCHES "AIX" AND NOT CYGWIN)
   set(LLVM_EXPORTED_SYMBOL_FILE)
   set(USE_VERSION_SCRIPT ${LLVM_HAVE_LINK_VERSION_SCRIPT})
 endif()
@@ -125,7 +125,7 @@ else()
   set(output_name "clang")
 endif()
 
-if (UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if (UNIX AND "${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
     set(CMAKE_AIX_EXPORT_ALL_SYMBOLS OFF)
     # libclang requires headers which need _ALL_SOURCE to build on AIX
     remove_definitions("-D_XOPEN_SOURCE=700")
@@ -186,7 +186,7 @@ if(ENABLE_SHARED)
     endif()
   endif()
   if (USE_VERSION_SCRIPT)
-    if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+    if ("${CMAKE_SYSTEM_NAME}" MATCHES "SunOS")
       include(CheckLinkerFlag)
       # The Solaris 11.4 linker supports a subset of GNU ld version scripts,
       # but requires a special option to enable it.

compiler-rt/cmake/config-ix.cmake

@@ -204,7 +204,7 @@ check_library_exists(stdc++ __cxa_throw "" COMPILER_RT_HAS_LIBSTDCXX)
 llvm_check_compiler_linker_flag(C "-Wl,-z,text" COMPILER_RT_HAS_Z_TEXT)
 llvm_check_compiler_linker_flag(C "-fuse-ld=lld" COMPILER_RT_HAS_FUSE_LD_LLD_FLAG)
 
-if(${CMAKE_SYSTEM_NAME} MATCHES "SunOS" AND LLVM_LINKER_IS_SOLARISLD)
+if("${CMAKE_SYSTEM_NAME}" MATCHES "SunOS" AND LLVM_LINKER_IS_SOLARISLD)
   set(VERS_COMPAT_OPTION "-Wl,-z,gnu-version-script-compat")
   llvm_check_compiler_linker_flag(C "${VERS_COMPAT_OPTION}" COMPILER_RT_HAS_GNU_VERSION_SCRIPT_COMPAT)
 endif()

compiler-rt/lib/asan/CMakeLists.txt

@@ -282,7 +282,7 @@ else()
   endif()
 
   # On AIX, we only need the static libraries.
-  if (NOT ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  if (NOT "${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   foreach(arch ${ASAN_SUPPORTED_ARCH})
     if (COMPILER_RT_HAS_VERSION_SCRIPT)
       if(WIN32)
@@ -392,7 +392,7 @@ add_compiler_rt_resource_file(asan_ignorelist asan_ignorelist.txt asan)
 # On AIX, static sanitizer libraries are not added to the DSO, so we need to put 
 # asan.link_with_main_exec.txt and asan_cxx.link_with_main_exec.txt to the build
 # and install dir for use in resolving undefined sanitizer symbols at runtime.
-if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if ("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   foreach(arch ${ASAN_SUPPORTED_ARCH})
     add_compiler_rt_cfg(asan_symbols_${arch} asan.link_with_main_exec.txt asan ${arch})
     add_compiler_rt_cfg(asan_cxx_symbols_${arch} asan_cxx.link_with_main_exec.txt asan ${arch})

libcxx/CMakeLists.txt

@@ -113,7 +113,7 @@ option(LIBCXX_ENABLE_MONOTONIC_CLOCK
 #
 # TODO TZDB make the default always ON when most platforms ship with the IANA
 # database.
-if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+if("${CMAKE_SYSTEM_NAME}" MATCHES "Linux")
   set(ENABLE_TIME_ZONE_DATABASE_DEFAULT ON)
 else()
   set(ENABLE_TIME_ZONE_DATABASE_DEFAULT OFF)
@@ -159,7 +159,7 @@ set(LIBCXX_TEST_PARAMS "" CACHE STRING
     "A list of parameters to run the Lit test suite with.")
 
 # TODO: Figure out how to build GoogleBenchmark on those platforms, and how to build when exceptions or RTTI is disabled
-if (WIN32 OR MINGW OR ANDROID OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX"
+if (WIN32 OR MINGW OR ANDROID OR "${CMAKE_SYSTEM_NAME}" MATCHES "AIX"
     OR NOT LIBCXX_ENABLE_LOCALIZATION
     OR NOT LIBCXX_ENABLE_THREADS
     OR NOT LIBCXX_ENABLE_FILESYSTEM
@@ -466,7 +466,7 @@ include(HandleLibcxxFlags)
 # 'config-ix' use them during feature checks. It also adds them to both
 # 'LIBCXX_COMPILE_FLAGS' and 'LIBCXX_LINK_FLAGS'
 
-if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if ("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   add_flags_if_supported("-mdefault-visibility-export-mapping=explicit")
   set(CMAKE_AIX_EXPORT_ALL_SYMBOLS OFF)
 endif()

libcxxabi/CMakeLists.txt

@@ -244,7 +244,7 @@ include(HandleLibcxxabiFlags)
 #===============================================================================
 
 # Configure target flags
-if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if ("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   add_flags_if_supported("-mdefault-visibility-export-mapping=explicit")
   set(CMAKE_AIX_EXPORT_ALL_SYMBOLS OFF)
 endif()
@@ -458,7 +458,7 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${LIBCXXABI_C_FLAGS}")
 
 # On AIX, avoid picking up VMX extensions(i.e. vec_malloc) which would change
 # the default alignment of the allocators here.
-if (UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if (UNIX AND "${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   add_definitions("-D_XOPEN_SOURCE=700")
 endif()
 

libcxxabi/src/CMakeLists.txt

@@ -37,7 +37,7 @@ else()
 endif()
 
 if (LIBCXXABI_ENABLE_THREADS AND (UNIX OR FUCHSIA) AND NOT (APPLE OR CYGWIN)
-    AND NOT (${CMAKE_SYSTEM_NAME} MATCHES "AIX"))
+    AND NOT ("${CMAKE_SYSTEM_NAME}" MATCHES "AIX"))
   list(APPEND LIBCXXABI_SOURCES
     cxa_thread_atexit.cpp
   )

libunwind/src/CMakeLists.txt

@@ -6,7 +6,7 @@ set(LIBUNWIND_CXX_SOURCES
     Unwind-seh.cpp
     )
 
-if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   list(APPEND LIBUNWIND_CXX_SOURCES
     Unwind_AIXExtras.cpp
     )

lldb/source/Host/CMakeLists.txt

@@ -7,7 +7,7 @@ if (APPLE AND LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY)
   endif()
 endif()
 
-if (UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if (UNIX AND "${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
   add_definitions("-D_ALL_SOURCE")
 endif()