fix incorrect application of visibility to Scrt1.o

commit de2b67f8d4 attempted to avoid
having vis.h affect crt files, but the Makefile variable used,
CRT_LIBS, refers to the final output copies in the lib directory, not
the copies in the crt build directory, and thus the -DCRT was not
applied.

while unlikely to be noticed, this regression probably broke
production of PIE executables whose main functions are not in the
executable but rather a shared library.

Makefile

@@ -104,7 +104,7 @@ NOSSP_SRCS = $(wildcard crt/*.c) \
 	src/ldso/dlstart.c src/ldso/dynlink.c
 $(NOSSP_SRCS:%.c=%.o) $(NOSSP_SRCS:%.c=%.lo): CFLAGS += $(CFLAGS_NOSSP)
 
-$(CRT_LIBS): CFLAGS += -DCRT
+$(CRT_LIBS:lib/%=crt/%): CFLAGS += -DCRT
 
 # This incantation ensures that changes to any subarch asm files will
 # force the corresponding object file to be rebuilt, even if the implicit