Pass the install-path into Makefile (#1200)

* Pass the install-path into Makefile, rather than having the Makefile
depend on PWD.

* Move the double-quotes be before the value, to be consistent with other
Makefiles.

test/nginx_system_test.sh

@@ -61,8 +61,9 @@ rm -rf "$SERVER_ROOT"
 mkdir -p "$SERVER_ROOT"
 export APACHE_DOC_ROOT="$SERVER_ROOT"
 
-mkdir -p $APACHE_DOC_ROOT
-cd "$MOD_PAGESPEED_DIR/src/install/" && make -f Makefile.tests setup_doc_root
+mkdir -p "$APACHE_DOC_ROOT"
+make -f "$APACHE_DOC_SRC/Makefile.tests" setup_doc_root \
+  INSTALL_DATA_DIR="$APACHE_DOC_SRC"
 
 # We need check and check_not before we source SYSTEM_TEST_FILE that provides
 # them.