ci: fix macos upstream pkgconf #1076

Job	Run time
jruby-head	1m 17s
ruby-head-valgrind (disable)	7m 41s
ruby-head (ubuntu, enable)	2m 51s
ruby-head (ubuntu, disable)	44s
ruby-head (windows, enable)	5m 26s
truffleruby-head (--disable-system-libraries --disable-static)	5m 11s
xmlsoft-head (ubuntu)	1m 29s
ruby-head (windows, disable)	3m 23s
truffleruby-head (--disable-system-libraries --enable-static)	3m 9s
html5lib-tests	1m 1s
xmlsoft-head (windows)	8m 35s
ruby-head (macos, enable)	41s
truffleruby-head (--enable-system-libraries)	2m 19s
xmlsoft-head (macos)	1m 53s
ruby-head (macos, disable)	2m 47s
xmlsoft-head-valgrind	6m 30s
	54m 57s

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