cmake: simplify the Saigo arm optimization disablement fix

Author: illwieckz

cmake/DaemonFlags.cmake

@@ -363,14 +363,12 @@ else()
 	endif()
 
 	if (NACL AND USE_NACL_SAIGO AND SAIGO_ARCH STREQUAL "arm")
-		# This should be set for every build type because build type flags
-		# are set after the other custom flags and then have the last word.
-		# DEBUG should already use -O0 anyway.
+		# Saigo produces broken arm builds when optimizing them.
 		# See: https://github.com/Unvanquished/Unvanquished/issues/3297
-		set_c_cxx_flag("-O0" DEBUG)
-		set_c_cxx_flag("-O0" RELEASE)
-		set_c_cxx_flag("-O0" RELWITHDEBINFO)
-		set_c_cxx_flag("-O0" MINSIZEREL)
+		# When setting this clang-specific option, we don't have to care
+		# about the ordering of -O options that may be introduced,
+		# all -O options added to the command line are ignored.
+		set_c_cxx_flag("-Xclang -disable-llvm-passes")
 	endif()
 
 	# Extra debug flags.