git-gui: Remove unused Cygwin compatibility code

Cygwin-distributed builds of git-gui have patched out the
Cygwin-specific compatibility code in the makefile before compiling
since at least the start of 2012 (specifically since at least Git
v1.7.9).  The compatibility code is clearly not necessary, so remove it
from the official git-gui code as well.

Signed-off-by: Adam Dinwoodie <adam@dinwoodie.org>

Author: me-and

Makefile

@@ -136,25 +136,11 @@ GITGUI_SCRIPT   := $$0
 GITGUI_RELATIVE :=
 GITGUI_MACOSXAPP :=
 
-ifeq ($(uname_O),Cygwin)
-	GITGUI_SCRIPT := `cygpath --windows --absolute "$(GITGUI_SCRIPT)"`
-
-	# Is this a Cygwin Tcl/Tk binary?  If so it knows how to do
-	# POSIX path translation just like cygpath does and we must
-	# keep libdir in POSIX format so Cygwin packages of git-gui
-	# work no matter where the user installs them.
-	#
-	ifeq ($(shell echo 'puts [file normalize /]' | '$(TCL_PATH_SQ)'),$(shell cygpath --mixed --absolute /))
-		gg_libdir_sed_in := $(gg_libdir)
-	else
-		gg_libdir_sed_in := $(shell cygpath --windows --absolute "$(gg_libdir)")
-	endif
-else
-	ifeq ($(exedir),$(gg_libdir))
-		GITGUI_RELATIVE := 1
-	endif
-	gg_libdir_sed_in := $(gg_libdir)
+ifeq ($(exedir),$(gg_libdir))
+	GITGUI_RELATIVE := 1
 endif
+gg_libdir_sed_in := $(gg_libdir)
+
 ifeq ($(uname_S),Darwin)
 	ifeq ($(shell test -d $(TKFRAMEWORK) && echo y),y)
 		GITGUI_MACOSXAPP := YesPlease