build-sys: add basic support for ./configure && make && make install

This adds the basic make support required by
https://github.com/cgwalters/build-api. CFLAGS, CXXFLAGS, DESTDIR variables are
supported:
   ./configure CFLAGS=... CXXFLAGS=... && make && make install DESTDIR=

Makefile

@@ -0,0 +1,5 @@
+all:
+	ninja -C build
+
+install:
+	DESTDIR=$(DESTDIR) ninja -C build

configure

@@ -0,0 +1,21 @@
+#!/bin/bash -e
+
+cflags=CFLAGS="$CFLAGS"
+cxxflags=CXXFLAGS="$CXXFLAGS"
+declare -a args
+j=0
+for i in "$@"; do
+    case "$i" in
+        CFLAGS=*)
+            cflags="$i";;
+        CXXFLAGS=*)
+            cxxflags="$i";;
+	*)
+	    args[$j]="$i"
+	    j=$((j+1))
+    esac
+done
+
+export "$cflags" "$cxxflags"
+set -x
+exec meson build "${args[@]}"