Disable matchcompiler on old python versions (#8352)

Author: pfultz2

cmake/findDependencies.cmake

@@ -49,7 +49,8 @@ if(NOT Python_Interpreter_FOUND)
     endif()
 else()
     if(${Python_VERSION} VERSION_LESS 3.7)
-        message(FATAL_ERROR "The minimum supported Python version is 3.7 - found ${Python_VERSION}")
+        message(WARNING "The minimum supported Python version is 3.7, found ${Python_VERSION} - disabling matchcompiler.")
+        set(USE_MATCHCOMPILER_OPT "Off")
     endif()
 endif()