Use $(CC) instead of gcc

Makefile

@@ -35,7 +35,7 @@ run-valgrind: bin/functest_$(subst /,_,$(SCHEME))
 ifeq ($(shell uname -s),Linux)
 	valgrind --leak-check=full --error-exitcode=1 $<
 else
-	echo "Valgrind not supported on this platform."
+	@echo "Valgrind not supported on this platform."
 endif
 
 bin/sanitizer_$(subst /,_,$(SCHEME)): test/$(dir $(SCHEME))functest.c $(wildcard $(SCHEME)/clean/*.c) $(wildcard $(SCHEME)/clean/*.h) | require_scheme
@@ -68,7 +68,7 @@ testvectors: bin/testvectors_$(subst /,_,$(SCHEME))
 
 bin/shared_$(subst /,_,$(SCHEME))_clean.so: $(wildcard $(SCHEME)/clean/*.c) | require_scheme
 	mkdir -p bin
-	gcc $(CFLAGS) \
+	$(CC) $(CFLAGS) \
 		-DPQCLEAN_NAMESPACE=$(shell echo PQCLEAN_$(subst -,,$(notdir $(SCHEME))) | tr a-z A-Z) \
 		-nostdlib \
 		-shared \
@@ -163,7 +163,7 @@ run-symbol-namespace: test/check_symbol_namespace.py | require_scheme
 
 .PHONY: run-testvectors-all
 run-testvectors-all: test/check_testvectors.py
-	for scheme in $(ALL_SCHEMES); do \
+	@for scheme in $(ALL_SCHEMES); do \
 	    python3 test/check_testvectors.py $$scheme || exit 1; \
 	done