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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<div class='path'>path: <a href='/guix/log/?id=1e6bd256a3d52e41719dbcd8ea5c0e90b187a738'>root</a>/<a href='/guix/log/tests?id=1e6bd256a3d52e41719dbcd8ea5c0e90b187a738'>tests</a>/<a href='/guix/log/tests/swh.scm?id=1e6bd256a3d52e41719dbcd8ea5c0e90b187a738'>swh.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/swh.scm?id=1e6bd256a3d52e41719dbcd8ea5c0e90b187a738&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-01-21 11:22:08 +0100'>2021-01-21</span></td><td><a href='/guix/commit/tests/swh.scm?id=5225732b9b54ffa92b9d199246b87dae666a3f77'>swh: Test proper handling of null visit snapshot URL.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-12-21 17:47:35 +0100'>2020-12-21</span></td><td><a href='/guix/commit/tests/swh.scm?id=9608f4003dedd8dfe99327c15668ca1a43ebd93b'>tests: Fix malformed JSON.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-02-27 23:29:30 +0100'>2020-02-27</span></td><td><a href='/guix/commit/tests/swh.scm?id=749b9582061f7d929be83a194040b63b41afec81'>swh: Adjust 'origin' test.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-09-02 15:25:01 +0200'>2019-09-02</span></td><td><a href='/guix/commit/tests/swh.scm?id=ba1c1853a79a5930ca7db7a6b368859f805df98d'>swh: Add hooks for rate limiting handling.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-09-02 15:25:01 +0200'>2019-09-02</span></td><td><a href='/guix/commit/tests/swh.scm?id=9323ab550f3bcb75fcaefbb20847595974702d5b'>tests: 'with-http-server' accepts multiple responses.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-07-22 11:53:39 +0200'>2019-07-22</span></td><td><a href='/guix/commit/tests/swh.scm?id=96f1cbeff84819f9886d15763b4c477cdecd7784'>swh: Add basic tests.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>