build-package: add new env. var. TERMUX_PACKAGES_DIRECTORIES

Can be set to the path to packages/ directories in other repos (like
unstable-package/packages/, termux-root-packages/packages/,
..). buildorder.py then searches these directories for packages and
dependencies

scripts/build/termux_step_setup_variables.sh

@@ -15,6 +15,7 @@ termux_step_setup_variables() {
 	: "${TERMUX_INSTALL_DEPS:="false"}"
 	: "${TERMUX_REPO_SIGNING_KEYS:="packages/apt/trusted.gpg packages/termux-keyring/grimler.gpg packages/termux-keyring/xeffyr.gpg"}"
 	: "${TERMUX_PKG_MAINTAINER:="Fredrik Fornwall @fornwall"}"
+	: "${TERMUX_PACKAGES_DIRECTORIES:="packages"}"
 
 	if [ -z ${TERMUX_REPO_URL+x} ]; then
 		TERMUX_REPO_URL=(https://termux.net)

scripts/build/termux_step_start_build.sh

@@ -49,7 +49,7 @@ termux_step_start_build() {
 			fi
 			mkdir -p /data/data/.built-packages
 			echo "$DEP_VERSION" > "/data/data/.built-packages/$PKG"
-		done<<<$(./scripts/buildorder.py -i "$TERMUX_PKG_BUILDER_DIR")
+		done<<<$(./scripts/buildorder.py -i "$TERMUX_PKG_BUILDER_DIR" $TERMUX_PACKAGES_DIRECTORIES)
 	elif [ "$TERMUX_SKIP_DEPCHECK" = false ] && [ "$TERMUX_INSTALL_DEPS" = false ]; then
 		# Build dependencies
 		while read PKG PKG_DIR; do
@@ -59,7 +59,7 @@ termux_step_start_build() {
 			echo "Building dependency $PKG if necessary..."
 			# Built dependencies are put in the default TERMUX_DEBDIR instead of the specified one
 			./build-package.sh -a $TERMUX_ARCH -s "${PKG_DIR}"
-		done<<<$(./scripts/buildorder.py "$TERMUX_PKG_BUILDER_DIR")
+		done<<<$(./scripts/buildorder.py "$TERMUX_PKG_BUILDER_DIR" $TERMUX_PACKAGES_DIRECTORIES)
 	fi
 
 	TERMUX_PKG_FULLVERSION=$TERMUX_PKG_VERSION

scripts/buildorder.py

@@ -236,7 +236,9 @@ def main():
     args = parser.parse_args()
     fast_build_mode = args.i
     package = args.package
-    packages_directories = args.package_dirs + ['packages']
+    packages_directories = args.package_dirs
+    if 'packages' not in packages_directories:
+        packages_directories.append('packages')
 
     if not package:
         full_buildorder = True