Fix build with GNU Make 4.3:

https://github.com/Aegisub/Aegisub/issues/171

Patch taken from upstream:

https://github.com/Aegisub/Aegisub/commit/6bd3f4c26b8fc1f76a8b797fcee11e7611d59a39

diff --git a/Makefile.target b/Makefile.target
--- a/Makefile.target
+++ b/Makefile.target
@@ -112,7 +112,7 @@ POST_FLAGS = $($@_FLAGS) -c -o $@ $<
 # Libraries contain all object files they depend on (but they may depend on other files)
 # Not using libtool on OS X because it has an unsilenceable warning about a
 # compatibility issue with BSD 4.3 (wtf)
-lib%.a: $$($$*_OBJ)
+lib%.a: $$($$(*F)_OBJ)
 	@$(BIN_MKDIR_P) $(dir $@)
 	$(BIN_AR) cru $@ $(filter %.o,$^)
 	$(BIN_RANLIB) $@
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<tr class='logheader'><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td class='logsubject'><a href='/guix/commit/tests/guix-pack.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a></td><td>Eric Bavier</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-lint.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh: Use the shell '!' keyword to negate command exit status
in place of 'if ...; then false; else true; fi'


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<tr class='logheader'><td><span title='2020-05-14 17:21:27 +0200'>2020-05-14</span></td><td class='logsubject'><a href='/guix/commit/tests/guix-pack.sh?id=80963744a242257921917df5a901dc343d3a93db'>store: 'mapm/accumulate-builds' preserves '%current-target-system'.</a></td><td>Ludovic Courtès</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
Fixes &lt;https://bugs.gnu.org/41182&gt;.

* guix/store.scm (mapm/accumulate-builds): Pass #:system and #:target to
'run-with-store'.
* tests/store.scm ("mapm/accumulate-builds, %current-target-system"):
New test.
* tests/guix-pack.sh: Add 'guix pack -d --target' test.


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<tr class='logheader'><td><span title='2020-03-31 00:06:36 +0200'>2020-03-31</span></td><td class='logsubject'><a href='/guix/commit/tests/guix-pack.sh?id=b771e0176a9cafaaf5fc279a7f3e5e3033b5fb4f'>pack: Adjust test to '--dry-run' changes.</a></td><td>Ludovic Courtès</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
This is a followup to 131f50cdc9dbb7183023f4dae759876a9e700bef.

* tests/guix-pack.sh: Use '--no-grafts' in conjunction with '-n' and '-d'.


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