Move GCC only flags to check

libultraship/Makefile

@@ -17,7 +17,6 @@ WARN := -Wall -Wextra -Werror \
 	-Wno-unused-function \
 	-Wno-parentheses \
 	-Wno-narrowing \
-	-Wno-error=stringop-overflow \
 	-Wno-missing-field-initializers \
 	-Wno-error=multichar \
 	-Wno-unused-command-line-argument \
@@ -27,7 +26,14 @@ WARN := -Wall -Wextra -Werror \
 	-Wno-deprecated-declarations
 
 CWARN :=
-CXXWARN := -Wno-deprecated-enum-enum-conversion -Wno-error=maybe-uninitialized
+CXXWARN := -Wno-deprecated-enum-enum-conversion
+
+# Detect if CXX is clang++ or g++, in this order.
+COMPILER_VERSION := $(shell $(CXX) --version)
+ifneq '' '$(findstring g++,$(COMPILER_VERSION))'
+	WARN += -Wno-error=stringop-overflow
+	CXXWARN += -Wno-error=maybe-uninitialized
+endif
 
 CXXFLAGS := $(WARN) $(CXXWARN) -std=c++20 -D_GNU_SOURCE -DENABLE_OPENGL -DSPDLOG_ACTIVE_LEVEL=0
 CFLAGS := $(WARN) $(CWARN) -std=c99 -D_GNU_SOURCE -DENABLE_OPENGL -DSPDLOG_ACTIVE_LEVEL=0