Makefile.am: fix portability issues

Commit a04f0b961333e1a19848d073d8c7db9c20b2a371 made me notice that
there is a portability issue in curl's top-level Makefile.am.

$< can only be used in rules that deal with .SUFFIXES.  Its use
for general prerequisites is a GNU make extension.

$< could be replaced by $?, but I think in an autotools context,
something like this is better:

Bug: https://curl.se/mail/lib-2022-05/0024.html
Closes #8861

diff --git a/Makefile.am b/Makefile.am
index f91c706feacb551e77408a8d2405147aa39b870c..d32e787c324706e8c0978dacc38ebd31e51c40bd 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -279,13 +279,13 @@ uninstall-hook:
        (cd docs && $(MAKE) uninstall)
        (cd docs/libcurl && $(MAKE) uninstall)
 
-ca-bundle: scripts/mk-ca-bundle.pl
+ca-bundle: $(srcdir)/scripts/mk-ca-bundle.pl
        @echo "generating a fresh ca-bundle.crt"
-       @perl $< -b -l -u lib/ca-bundle.crt
+       @perl $(srcdir)/scripts/mk-ca-bundle.pl -b -l -u lib/ca-bundle.crt
 
-ca-firefox: scripts/firefox-db2pem.sh
+ca-firefox: $(srcdir)/scripts/firefox-db2pem.sh
        @echo "generating a fresh ca-bundle.crt"
-       $< lib/ca-bundle.crt
+       $(srcdir)/scripts/firefox-db2pem.sh lib/ca-bundle.crt
 
 checksrc:
        (cd lib && $(MAKE) checksrc)