compat/vcbuild: possibly reuse Git for Windows' SDK's NuGet

In Git for Windows' SDK, there is already a script to package Git for
Windows as a NuGet package, downloading nuget.exe if needed.

Let's just fall back to using that executable (if it is there) if
nuget.exe was not found in the PATH.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

compat/vcbuild/Makefile

@@ -7,14 +7,18 @@ INST_LIB=$(INST)/lib
 INST_BIN=$(INST)/bin
 
 PKGDIR=GEN.PKGS
+NUGET ?= nuget.exe
+ifneq ($(shell $(NUGET) help 2>/dev/null; echo $$?),0)
+	NUGET := /usr/src/build-extra/nuget/nuget.exe
+endif
 
 ##################################################################
 all:	unpack expat libssh libssh_redist curl curl_redist openssl zlib \
 	libiconv libiconv_redist
 
 unpack:
 	[ -d $(PKGDIR) ] || mkdir $(PKGDIR)
-	nuget.exe restore packages.config -ConfigFile nuget.config \
+	"$(NUGET)" restore packages.config -ConfigFile nuget.config \
 		-NonInteractive -OutputDirectory $(PKGDIR)
 
 insdir: