Support the tools scripted in perl.

There is one subtlety in perl/Makefile: The $(prefix) may contain a drive
letter-colon combination. But unfortunately, the perl scripts contain
a stance that splits the path at colons to find Git.pm. For this reason,
we convert the path to the MSYS style, which does not have the colon.

Makefile

@@ -424,6 +424,7 @@ ifeq ($(uname_S),IRIX64)
 endif
 ifneq (,$(findstring MINGW,$(uname_S)))
 	SHELL_PATH = $(shell cd /bin && pwd -W)/sh
+	PERL_PATH = $(shell cd /bin && pwd -W)/perl
 	NO_MMAP=YesPlease
 	NO_PREAD=YesPlease
 	NO_OPENSSL=YesPlease
@@ -440,6 +441,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_STRTOUMAX = YesPlease
 	NO_SYMLINKS=YesPlease
 	NO_SVN_TESTS=YesPlease
+	NO_PERL_MAKEMAKER=YesPlease
 	COMPAT_CFLAGS += -DNO_ETC_PASSWD -DNO_ST_BLOCKS -DSTRIP_EXTENSION=\".exe\" -I compat
 	COMPAT_OBJS += compat/mingw.o compat/fnmatch.o
 	EXTLIBS += -lws2_32 -lregex

perl/Makefile

@@ -16,7 +16,11 @@ clean:
 	$(RM) $(makfile).old
 
 ifdef NO_PERL_MAKEMAKER
-instdir_SQ = $(subst ','\'',$(prefix)/lib)
+# We exploit that /bin/sh transforms the DOS-Stype path in TEMP into
+# the MSYS style pseudo-mount form.
+# This colon-free from is needed because our perl scripts look at
+# $(instdir_SQ) and split it at colons.
+instdir_SQ = $(subst ','\'',$(shell cmd /x/d/c "set TEMP=$(prefix)/lib && sh -c 'echo \$$TEMP'"))
 $(makfile): ../GIT-CFLAGS Makefile
 	echo all: > $@
 	echo '	:' >> $@