make: use shell-command assignment instead of $(eval ...)
This is portable between BSD and GNU make.
As of this change, our Makefile appears to work in both BSD and GNU
make, with the caveat that the test-% and testpy-% wildcard rules
don't work on BSD make. That said, this still seems worthwhile because
it lets the buildbots work more consistently across platforms.
--- a/Makefile Thu Apr 21 10:10:48 2016 -0400
+++ b/Makefile Thu Apr 21 10:11:20 2016 -0400
@@ -6,7 +6,7 @@
export PREFIX=/usr/local
PYTHON=python
-$(eval HGROOT := $(shell pwd))
+HGROOT != pwd
HGPYTHONS ?= $(HGROOT)/build/pythons
PURE=
PYFILES:=$(shell find mercurial hgext doc -name '*.py')