Workaround for homebrew gettext when building xz

The xz autogen.sh script requires the autopoint tool which is provided by the gettext homebrew package on macOS but it's not installed into PATH by default. This MR adds a little workaround to look for the homebrew version of gettext and use its autopoint if it exists.

recipes/xz/recipe.sh

@@ -13,8 +13,17 @@ function recipe_update {
 
 function recipe_build {
     export CFLAGS="-static"
+    
+    # autogen.sh requires autopoint which is provided by the gettext homebrew
+    # formula on macOS. Unfortunately, homebrew does not install it into PATH
+    # because macOS provides the BSD gettext library. So we make sure to include
+    # it in PATH, preceding the default BSD version.
+    if [[ "$(uname)" == "Darwin" ]]; then
+        export PATH="/usr/local/opt/gettext/bin:$PATH"
+    fi
 
     ./autogen.sh
+
     chmod +w build-aux/config.sub
     wget -O build-aux/config.sub http://git.savannah.gnu.org/cgit/config.git/plain/config.sub
     ./configure \