libgcompat: Add and use a macro for defining symbol aliases

* Prefer providing the underscore-prefixed symbol as the strong
  definition.
* Do not use a weak alias if the alias is also underscore-prefixed.
* Make libgcompat objects depend on the new header.

[NOTE: I originally took the weak_alias macro from musl's libc.h, but
       it's trivial and the same pattern already in use. If desired, I
       can add the musl copyright notice.]

Signed-off-by: Samuel Holland <samuel@sholland.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 6c532fd..b941dcf 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,5 @@
+LIBGCOMPAT_INCLUDE = \
+	libgcompat/alias.h
 LIBGCOMPAT_SRC = \
 	libgcompat/backtrace.c		\
 	libgcompat/dlmopen.c		\
@@ -33,6 +35,8 @@ ${LIBGCOMPAT_NAME}: ${LIBGCOMPAT_OBJ}
 	$(CC) -o ${LIBGCOMPAT_NAME} -Wl,-soname,${LIBGCOMPAT_NAME} \
 		-shared ${LIBGCOMPAT_OBJ}
 
+${LIBGCOMPAT_OBJ}: ${LIBGCOMPAT_INCLUDE}
+
 ${LOADER_NAME}: ${LOADER_OBJ}
 	$(CC) -o ${LOADER_NAME} -fPIE -static ${LOADER_OBJ}