cmake: forward the macOS deployment target to the TIME function test

When using newer Xcode releases, older `gfortran` may be given a
deployment target that is not understood if the host is on a new enough
version. Forward the deployment target from the main project to the
testing project to check with similar settings as the main project.

Author: mathstuf

CMAKE/CheckTimeFunction.cmake

@@ -11,6 +11,8 @@ macro(CHECK_TIME_FUNCTION FUNCTION VARIABLE)
     ${PROJECT_BINARY_DIR}/INSTALL
     ${PROJECT_SOURCE_DIR}/INSTALL
     TIMING secondtst_${FUNCTION}
+    CMAKE_FLAGS
+      -DCMAKE_OSX_DEPLOYMENT_TARGET:STRING=${CMAKE_OSX_DEPLOYMENT_TARGET}
     OUTPUT_VARIABLE OUTPUT)
 
     if(RES)