Ports: check for native python3 installation, add build script

For python3 cross compilation, a native installation of python3 is
needed. This patch adds a build script for python3 to the toolchain
and informs the user to run that script if the python port is build
and no native python3 with the same major and minor version is
being found.

Ports/python-3.6/package.sh

@@ -1,4 +1,7 @@
 #!/bin/bash ../.port_include.sh
+
+source version.sh
+
 port=python-3.6
 version=3.6
 workdir=Python-3.6.0
@@ -6,6 +9,18 @@ useconfigure=true
 configopts="--build=i686 --without-threads --enable-optimizations"
 makeopts="-j$(nproc) build_all"
 installopts="-j$(nproc) build_all"
-files="https://www.python.org/ftp/python/3.6.0/Python-3.6.0.tar.xz Python-3.6.0.tar.xz"
+files="${PYTHON_URL} ${PYTHON_ARCHIVE}"
 
 export CONFIG_SITE=$(pwd)/config.site
+
+if [ -x "$(command -v python3)" ]; then
+  # check if major and minor version of python3 are matching
+  if python3 -c "import sys;sys.exit('.'.join(str(n) for n in sys.version_info[:2]) in '$PYTHON_VERSION')"; then
+    echo 'Error: python3 version does not match needed version to build:' $PYTHON_VERSION >&2
+    echo 'Please build python3.6 with Toolchain/BuildPython.sh !' >&2
+    exit 1
+  fi
+else
+    echo 'Error: python3 is not installed, please build python3.6 with Toolchain/BuildPython.sh !' >&2
+    exit 1
+fi

Ports/python-3.6/version.sh

@@ -0,0 +1,4 @@
+PYTHON_VERSION="3.6.0"
+PYTHON_MD5SUM="82b143ebbf4514d7e05876bed7a6b1f5"
+PYTHON_ARCHIVE="Python-$PYTHON_VERSION.tar.xz"
+PYTHON_URL="https://www.python.org/ftp/python/$PYTHON_VERSION/${PYTHON_ARCHIVE}"

Toolchain/BuildPython.sh

@@ -0,0 +1,62 @@
+#!/bin/bash
+set -e
+
+# This file will need to be run in bash, for now.
+
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+
+echo "$DIR"
+
+TARGET=i686-pc-serenity
+PREFIX="$DIR/Local"
+SYSROOT="$DIR/../Root"
+
+source "$DIR/../Ports/python-3.6/version.sh"
+
+echo PYTHON_VERSION is "$PYTHON_VERSION"
+echo PYTHON_URL is "$PYTHON_URL"
+
+echo PREFIX is "$PREFIX"
+echo SYSROOT is "$SYSROOT"
+
+mkdir -p "$DIR/Tarballs"
+
+source "$DIR/UseIt.sh"
+
+pushd "$DIR/Tarballs"
+    if [ ! -e "$PYTHON_ARCHIVE" ]; then
+        curl -O "$PYTHON_URL"
+    else
+        echo "Skipped downloading Python-$PYTHON_VERSION"
+    fi
+
+    md5="$(md5sum $PYTHON_ARCHIVE | cut -f1 -d' ')"
+    echo "python md5='$md5'"
+    if  [ "$md5" != "$PYTHON_MD5SUM" ] ; then
+        echo "python md5 sum mismatching, please run script again."
+        rm $PYTHON_ARCHIVE
+        exit 1
+    fi
+
+    if [ ! -d "Python-$PYTHON_VERSION" ]; then
+        echo "Extracting python..."
+        tar -xf "$PYTHON_ARCHIVE"
+    else
+        echo "Skipped extracting python"
+    fi
+popd
+
+mkdir -p "$PREFIX"
+mkdir -p "$DIR/Build/python"
+
+if [ -z "$MAKEJOBS" ]; then
+    MAKEJOBS=$(nproc)
+fi
+
+pushd "$DIR/Build/"
+    pushd python
+        "$DIR"/Tarballs/Python-$PYTHON_VERSION/configure --prefix="$PREFIX" || exit 1
+        make -j "$MAKEJOBS" || exit 1
+        make install || exit 1
+    popd
+popd