CheckSupportSSE2: Fix sse flags unexpected propagation (#1721)

Set function will affects all variables in current directory. If sse
flags are added in CheckSupportSSE2.cmake, they will remain in
Findminizip-ng.cmake which will cause liblzma cannot be detected. This
patch keep CMAKE_REQUIRED_FLAGS being changed only in current file
scope. This patch has been tested on riscv64.

Signed-off-by: Letu Ren <fantasquex@gmail.com>

Signed-off-by: Letu Ren <fantasquex@gmail.com>
Co-authored-by: Doug Walker <doug.walker@autodesk.com>

share/cmake/utils/CheckSupportSSE2.cmake

@@ -3,6 +3,8 @@
 
 include(CheckCXXSourceCompiles)
 
+set(_cmake_required_flags_old "${CMAKE_REQUIRED_FLAGS}")
+
 if(NOT CMAKE_SIZE_OF_VOID_P EQUAL 8)
     # As CheckCXXCompilerFlag implicitly uses CMAKE_CXX_FLAGS some custom flags could trigger
     # unrelated warnings causing a detection failure. So, the code disables all warnings to focus
@@ -27,4 +29,7 @@ check_cxx_source_compiles ("
     }"
     HAVE_SSE2)
 
+set(CMAKE_REQUIRED_FLAGS "${_cmake_required_flags_old}")
+unset(_cmake_required_flags_old)
+
 mark_as_advanced(HAVE_SSE2)