diff -r 1e332d63bd96 -r fa378e035b81 doc/building.md
--- a/doc/building.md	Fri Aug 24 08:17:23 2018 +0200
+++ b/doc/building.md	Fri Aug 24 09:38:11 2018 +0200
@@ -1018,6 +1018,51 @@
   * If the X11 libraries are not properly detected by `configure`, you can
     point them out by `--with-x`.
 
+### Creating And Using Sysroots With qemu-deboostrap
+
+Fortunately, you can create sysroots for foreign architectures with tools
+provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
+create the *target* system chroot, which would have the native libraries and headers
+specific to that *target* system. After that, we can use the cross-compiler on the *build*
+system, pointing into chroot to get the build dependencies right. This allows building
+for foreign architectures with native compilation speed.
+
+For example, cross-compiling to AArch64 from x86_64 could be done like this:
+
+  * Install cross-compiler on the *build* system:
+```
+apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
+```
+
+  * Create chroot on the *build* system, configuring it for *target* system:
+```
+sudo qemu-debootstrap --arch=arm64 --verbose \
+       --include=fakeroot,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng12-dev \
+       --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
+```
+
+  * Configure and build with newly created chroot as sysroot/toolchain-path:
+```
+CC=aarch64-linux-gnu-gcc CXX=aarch64-linux-gnu-g++ sh ./configure --openjdk-target=aarch64-linux-gnu --with-sysroot=/chroots/arm64/ --with-toolchain-path=/chroots/arm64/
+make images
+ls build/linux-aarch64-normal-server-release/
+```
+
+The build does not create new files in that chroot, so it can be reused for multiple builds
+without additional cleanup.
+
+Architectures that are known to successfully cross-compile like this are:
+
+  Target        `CC`                      `CXX`                       `--arch=...` `--openjdk-target=...`
+  ------------  ------------------------- --------------------------- ------------ ----------------------
+  x86           default                   default                     i386         i386-linux-gnu
+  armhf         gcc-arm-linux-gnueabihf   g++-arm-linux-gnueabihf     armhf        arm-linux-gnueabihf
+  aarch64       gcc-aarch64-linux-gnu     g++-aarch64-linux-gnu       arm64        aarch64-linux-gnu
+  ppc64el       gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu   ppc64el      powerpc64le-linux-gnu
+  s390x         gcc-s390x-linux-gnu       g++-s390x-linux-gnu         s390x        s390x-linux-gnu
+
+Additional architectures might be supported by Debian/Ubuntu Ports.
+
 ### Building for ARM/aarch64
 
 A common cross-compilation target is the ARM CPU. When building for ARM, it is