Remove options not known to older gcc

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 3e3bd1f..49bd878 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -3363,7 +3363,7 @@
 
     msg "build: TF-M config, gcc native build"
     make clean
-    make lib CC="gcc" CFLAGS="-Os -std=c99 -Werror -Wall -Wextra -Wwrite-strings -Wpointer-arith -Wimplicit-fallthrough -Wshadow -Wvla -Wformat=2 -Wno-format-nonliteral -Wshadow -Wformat-signedness -Wformat-overflow=2 -Wformat-truncation -Wlogical-op"
+    make lib CC="gcc" CFLAGS="-Os -std=c99 -Werror -Wall -Wextra -Wwrite-strings -Wpointer-arith -Wshadow -Wvla -Wformat=2 -Wno-format-nonliteral -Wshadow -Wformat-signedness -Wlogical-op"
 }
 
 component_build_aes_variations() { # ~45s