BuildSystem: Rewrite port compilation system

Now ports define some environment variables, and call a unified bash
script that handles configuration, recompilation and installation.

If a port uses non-configure buildsystem, port script can also specify
custom build and install step.

ports/doom/build.sh

@@ -1,33 +1,17 @@
-#!/bin/sh
+#!/bin/bash ../install.sh
 
-if [ -z $BANAN_ARCH ]; then
-	echo  "You must set the BANAN_ARCH environment variable" >&2
-	exit 1
-fi
+NAME='doom'
+VERSION='git'
+DOWNLOAD_URL="https://github.com/ozkl/doomgeneric.git#613f870b6fa83ede448a247de5a2571092fa729d"
 
-if [ -z $BANAN_SYSROOT ]; then
-	echo  "You must set the BANAN_ARCH environment variable" >&2
-	exit 1
-fi
+build() {
+	if [ ! -f doom1.wad ]; then
+		wget https://distro.ibiblio.org/slitaz/sources/packages/d/doom1.wad || exit 1
+	fi
+	make --directory doomgeneric --file Makefile.banan_os -j$(nproc) || exit 1
+}
 
-cd $(dirname $(realpath $0))
-
-if [ ! -d "doomgeneric" ]; then
-	git clone https://github.com/ozkl/doomgeneric.git
-	cd doomgeneric
-	git checkout 613f870b6fa83ede448a247de5a2571092fa729d
-	for patch in ../patches/*; do
-		git am "$patch"
-	done
-	cd ..
-
-	grep -qxF doom ../installed || echo doom >> ../installed
-fi
-
-if [ ! -f doom1.wad ]; then
-	wget https://distro.ibiblio.org/slitaz/sources/packages/d/doom1.wad
-fi
-
-make --directory doomgeneric/doomgeneric --file Makefile.banan_os -j $(nproc)
-cp "doomgeneric/doomgeneric/build-${BANAN_ARCH}/doomgeneric" "${BANAN_SYSROOT}/bin/doom"
-cp doom1.wad $BANAN_SYSROOT/home/user/
+install() {
+	cp doomgeneric/build/doom "${BANAN_SYSROOT}/bin/" || exit 1
+	cp ./doom1.wad "$BANAN_SYSROOT/home/user/" || exit 1
+}