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><td><span title='2022-03-09 23:38:18 +0100'>2022-03-09</span></td><td><a href='/guix/commit/gnu/packages/hurd.scm?id=a9a64c19830ac0fc92bf9eac5d83751df683ff31'>gnu: hurd: Adjust to the transition from "--system" to "gnu.system".</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 0dc019e19a23fea614be5623360849ab9bc35e74, which
inadvertently led the Hurd to fail to boot.

* gnu/packages/hurd.scm (hurd)[arguments]: In 'create-runsystem' phase,
expect "gnu.system=" instead of "--system=".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-15 22:43:29 +0100'>2022-02-15</span></td><td><a href='/guix/commit/gnu/packages/hurd.scm?id=6ec07f6b38f8839f837590823f181a37b016c6b0'>gnu: hurd: Remove leftover export.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/hurd.scm: Remove 'hurd-triplet?' export.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>