build: Split libmd dependency due to MD5 functions from SHA requirements

To be able to rework the md5 deprecation logic, we need to detangle when
we depend on libmd due to requiring MD5 functions, which might be
otherwise provided by libc, or when we require SHA functions for the
internal getentropy() implementation.

configure.ac

@@ -110,7 +110,7 @@ AC_SEARCH_LIBS([dlsym], [dl], [
 ])
 AC_SEARCH_LIBS([MD5Update], [md], [
   AS_IF([test "x$ac_cv_search_MD5Update" != "xnone required"], [
-    LIBBSD_LIBS="$LIBBSD_LIBS $ac_cv_search_MD5Update"
+    MD5_LIBS="$MD5_LIBS $ac_cv_search_MD5Update"
   ])
 ], [
   AC_MSG_ERROR([cannot find required MD5 functions in libc or libmd])
@@ -250,6 +250,7 @@ AC_CHECK_FUNCS([clearenv dirfd fopencookie __fpurge \
                 pstat_getproc sysconf])
 AM_CONDITIONAL([HAVE_GETENTROPY], [test "x$ac_cv_func_getentropy" = "xtrue"])
 
+AC_SUBST([MD5_LIBS])
 AC_SUBST([LIBBSD_LIBS])
 
 AC_CONFIG_FILES([

src/Makefile.am

@@ -52,6 +52,7 @@ libbsd_la_DEPENDENCIES = \
 	$(libbsd_la_included_sources) \
 	libbsd.map
 libbsd_la_LIBADD = \
+	$(MD5_LIBS) \
 	$(LIBBSD_LIBS) \
 	$(nil)
 libbsd_la_LDFLAGS = \

src/libbsd-overlay.pc.in

@@ -8,5 +8,5 @@ Description: Utility functions from BSD systems (overlay)
 Version: @VERSION@
 URL: https://libbsd.freedesktop.org/
 Libs: -L${libdir} -lbsd
-Libs.private: @LIBBSD_LIBS@
+Libs.private: @LIBBSD_LIBS@ @MD5_LIBS@
 Cflags: -isystem ${includedir}/bsd -DLIBBSD_OVERLAY

src/libbsd.pc.in

@@ -8,5 +8,5 @@ Description: Utility functions from BSD systems
 Version: @VERSION@
 URL: https://libbsd.freedesktop.org/
 Libs: -L${libdir} -lbsd
-Libs.private: @LIBBSD_LIBS@
+Libs.private: @LIBBSD_LIBS@ @MD5_LIBS@
 Cflags: -I${includedir}