install-libs: depend on the "toollibs"

Before symlinking libg.a, we need the symlink source `libmsys-2.0.a`: in
MSYS2, we copy by default (if we were creating Unix-style symlinks, the
target would not have to exist before symlinking, but when copying we do
need the source _right away_).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

winsup/cygwin/Makefile.am

@@ -699,7 +699,7 @@ man_MANS = regex/regex.3 regex/regex.7
 install-exec-hook: install-libs
 install-data-local: install-headers install-ldif
 
-install-libs:
+install-libs: install-toollibDATA
 	@$(MKDIR_P) $(DESTDIR)$(bindir)
 	$(INSTALL_PROGRAM) $(NEW_DLL_NAME) $(DESTDIR)$(bindir)/$(DLL_NAME)
 	@$(MKDIR_P) $(DESTDIR)$(toollibdir)