Make bitness to be detected on Windows

Required to run script from Git bash. MSVC_ARCH is to
be provided by either configuration or environment.

bundle/bundle-linux.sh

@@ -63,6 +63,18 @@ if [ "${KERNEL_NAME}" == "Linux" ]; then
 elif [ "${KERNEL_NAME}" == "Darwin" ]; then
   MACHINE_TYPE="x86_64"
   BITNESS="64"
+elif [[ "${KERNEL_NAME}" == "MINGW"* ]]; then
+  if [ -z "${MSVC_ARCH}" ]; then
+    echo "ERROR: On Windows MSVC_ARCH is to be set to either x86 or x64."
+    exit 1
+  fi
+  if [ "${MSVC_ARCH}" == "x86" ]; then
+    BITNESS="64"
+  elif [ "${MSVC_ARCH}" == "x86" ]; then
+    BITNESS="32"
+  fi
+  # TODO(sergey): Detect MSVC install somehow.
+  "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" "${MSVC_ARCH}"
 fi
 
 SVN_BENCHMARK_URL="https://svn.blender.org/svnroot/bf-blender/trunk/lib/benchmarks/cycles/"