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=d4d1c311fc318a5b907c4701b4c7f0b55d2495af'>root</a>/<a href='/guix/log/build-aux?id=d4d1c311fc318a5b907c4701b4c7f0b55d2495af'>build-aux</a>/<a href='/guix/log/build-aux/compile-as-derivation.scm?id=d4d1c311fc318a5b907c4701b4c7f0b55d2495af'>compile-as-derivation.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/build-aux/compile-as-derivation.scm?id=d4d1c311fc318a5b907c4701b4c7f0b55d2495af&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-09-02 15:43:51 +0200'>2018-09-02</span></td><td><a href='/guix/commit/build-aux/compile-as-derivation.scm?id=20cbd4f5f4d08bc26c22eb40b6c1e55b02e93f23'>compile-as-derivation: Adjust %load-compiled-path.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-06-09 12:02:27 +0200'>2018-06-09</span></td><td><a href='/guix/commit/build-aux/compile-as-derivation.scm?id=75e24d7b0e19ab2164aecb340e82d07d2b9714e7'>pull: Install the new Guix in a profile.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-06-09 12:02:27 +0200'>2018-06-09</span></td><td><a href='/guix/commit/build-aux/compile-as-derivation.scm?id=8a0d9bc8a3f153159d9e239a151c0fa98f1e12d8'>self: Produce a complete package with the 'guix' command.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-04-08 17:48:25 +0200'>2018-04-08</span></td><td><a href='/guix/commit/build-aux/compile-as-derivation.scm?id=2cfc8d69644af6c53fed9128425e8ff70ad4509f'>build: Add 'as-derivation' target.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>