avoid a non-portable shell construct ("builddir=$(shell pwd)") so that the

makefile created by apxs -g works on more systems

it was broken on at least AIX and Tru64


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95646 13f79535-47bb-0310-9956-ffa450edef68