Makefile: support CFLAGS and LDFLAGS for the vc/v.c to v bootstrap.

Author: spytheman

Makefile

@@ -1,10 +1,12 @@
 CC ?= cc
 VFLAGS ?=
+CFLAGS ?=
+LDFLAGS ?=
 
 all:
 	rm -rf vc/
 	git clone --depth 1 --quiet https://github.com/vlang/vc
-	$(CC) -std=gnu11 -w -I ./thirdparty/stdatomic/nix -o v1 vc/v.c -lm -lexecinfo -lpthread
+	$(CC) $(CFLAGS) -std=gnu11 -w -I ./thirdparty/stdatomic/nix -o v1 vc/v.c -lm -lexecinfo -lpthread $(LDFLAGS)
 	./v1 -no-parallel -o v2 $(VFLAGS) cmd/v
 	./v2 -o v $(VFLAGS) cmd/v
 	rm -rf v1 v2 vc/