Make SANITIZER_MIN_OSX_VERSION a cache variable (llvm#74394)

It is desirable to be able to configure the `-mmacosx-version-min` flag
for the sanitizers, but this flag was never made a CACHE variable in
cmake.

By doing this, it will allow developers to select different minimum
versions, which results in different interceptors being enabled or
disabled on their platforms. This version can now persist between cmake
runs, so it can be remembered by cmake, and edited in the cache file.

compiler-rt/cmake/config-ix.cmake

@@ -461,29 +461,34 @@ if(APPLE)
     set(ORC_SUPPORTED_OS osx)
   endif()
 
-  # Note: In order to target x86_64h on OS X the minimum deployment target must
-  # be 10.8 or higher.
   set(DEFAULT_SANITIZER_MIN_OSX_VERSION 10.10)
   set(DARWIN_osx_MIN_VER_FLAG "-mmacosx-version-min")
   if(NOT SANITIZER_MIN_OSX_VERSION)
     string(REGEX MATCH "${DARWIN_osx_MIN_VER_FLAG}=([.0-9]+)"
            MACOSX_VERSION_MIN_FLAG "${CMAKE_CXX_FLAGS}")
     if(MACOSX_VERSION_MIN_FLAG)
-      set(SANITIZER_MIN_OSX_VERSION "${CMAKE_MATCH_1}")
+      set(MIN_OSX_VERSION "${CMAKE_MATCH_1}")
     elseif(CMAKE_OSX_DEPLOYMENT_TARGET)
-      set(SANITIZER_MIN_OSX_VERSION ${CMAKE_OSX_DEPLOYMENT_TARGET})
+      set(MIN_OSX_VERSION ${CMAKE_OSX_DEPLOYMENT_TARGET})
     else()
-      set(SANITIZER_MIN_OSX_VERSION ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
+      set(MIN_OSX_VERSION ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
     endif()
-    if(SANITIZER_MIN_OSX_VERSION VERSION_LESS "10.7")
+
+    # Note: In order to target x86_64h on OS X the minimum deployment target must
+    # be 10.8 or higher.
+    if(MIN_OSX_VERSION VERSION_LESS "10.7")
       message(FATAL_ERROR "macOS deployment target '${SANITIZER_MIN_OSX_VERSION}' is too old.")
     endif()
-    if(SANITIZER_MIN_OSX_VERSION VERSION_GREATER ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
+    if(MIN_OSX_VERSION VERSION_GREATER ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
       message(WARNING "macOS deployment target '${SANITIZER_MIN_OSX_VERSION}' is too new, setting to '${DEFAULT_SANITIZER_MIN_OSX_VERSION}' instead.")
-      set(SANITIZER_MIN_OSX_VERSION ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
+      set(MIN_OSX_VERSION ${DEFAULT_SANITIZER_MIN_OSX_VERSION})
     endif()
+
   endif()
 
+  set(SANITIZER_MIN_OSX_VERSION "${MIN_OSX_VERSION}" CACHE STRING
+    "Minimum OS X version to target (e.g. 10.10) for sanitizers.")
+
   # We're setting the flag manually for each target OS
   set(CMAKE_OSX_DEPLOYMENT_TARGET "")