Set -ffp-contract=off compiler flag for GCC >= 11

Replace the previous workaround of setting -fno-tree-loop-vectorize for
a GCC optimization bug.

(Beep6581#6384)

CMakeLists.txt

@@ -45,10 +45,14 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION
 endif()
 
 # Warning for GCC vectorization issues, which causes problems #5749 and #6384:
-if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND ((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "10.0" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.2") OR (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "11.0")))
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "10.0" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.2")
     message(STATUS "WARNING: gcc ${CMAKE_CXX_COMPILER_VERSION} is known to miscompile RawTherapee when using -ftree-loop-vectorize, forcing the option to be off")    
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-tree-loop-vectorize")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-tree-loop-vectorize")
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "11.0")
+    message(STATUS "WARNING: gcc ${CMAKE_CXX_COMPILER_VERSION} is known to miscompile RawTherapee when using --ffp-contract=fast, forcing the option to be off")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffp-contract=off")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ffp-contract=off")
 endif()
 
 # We might want to build using the old C++ ABI, even when using a new GCC