Fix filtering of FORTIFY_SOURCE flags (#119719)

On Fedora and RHEL, when building the VMR (and runtime) we provide
additional CFLAGS/CXXFLAGS to the build, including this set:

    -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS

This is filtered incorrectly in eng/native/configureplatform.cmake,
resulting in this CFLAG:

    -Wp,-Wp,-D_GLIBCXX_ASSERTIONS

This is invalid and makes the build fail.

Author: omajid

eng/native/configureplatform.cmake

@@ -511,6 +511,8 @@ endif()
 string(TOLOWER "${CMAKE_BUILD_TYPE}" LOWERCASE_CMAKE_BUILD_TYPE)
 if(LOWERCASE_CMAKE_BUILD_TYPE STREQUAL debug)
     # Clear _FORTIFY_SOURCE=2, if set
+    string(REPLACE "-Wp,-D_FORTIFY_SOURCE=2 " "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    string(REPLACE "-Wp,-D_FORTIFY_SOURCE=2 " "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
     string(REPLACE "-D_FORTIFY_SOURCE=2 " "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
     string(REPLACE "-D_FORTIFY_SOURCE=2 " "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
 endif()