Add qemu_multiarch_testing/

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

qemu_multiarch_testing/README

@@ -0,0 +1,63 @@
+How to test build using Aboriginal Linux system images.
+
+* Put a source tree into hdc.dir/.
+For example, this should work:
+git clone git://busybox.net/var/lib/git/busybox.git
+
+* Run ./make-hdc-img.sh: it will generate ext2 image file,
+hdc.img, from hdc.dir/* data. This requires root for loop mount.
+
+* Download and unpack, or build from source and unpack
+one or more system-image-ARCH directories into this directory
+(the one which contains this README).
+
+* Run: ./parallel-build-hdc-img.sh system-image-DIR1 system-image-DIR2...
+(background it if you don't want to see "Waiting to finish" thing).
+This runs build in several qemu virtual machines in parallel.
+
+* Observe system-image-*.log file(s) with growing log of the build.
+
+There is no automated detection of errors for now: you need to examine
+logs yourself.
+
+Log files will also contain uuencoded (or if all else fails, od -tx1'ed)
+binary, if build was successful.
+
+To debug a build problem in one of the sandboxes, change keep_hdb
+to "keep_hdb=true" in parallel-build-hdc-img.sh
+- this preserves system-image-ARCH/hdb.img after the build,
+so you can go into system-image-ARCH and run
+"HDB=hdb.img ./dev-environment.sh" to debug the problem.
+
+You can also run "./parallel-build-hdc-img.sh -s system-image-ARCH"
+- single mode, output is to screen and serial input is from keyboard.
+
+If hdc.dir/bin/busybox-$ARCH exists, it will be used during build
+to supply additional tools.
+
+For me, the following system images worked:
+system-image-armv4l
+system-image-armv4tl
+system-image-armv5l
+    od is buggy on arm*:
+    # echo Hello-hello-hello-hello | od -b
+    0000000 110 145 154 154 157 055 150 145 154 154 157 055 150 145 154 154
+    0000000 157 055 150 145 154 154 157 012
+    0000000
+system-image-i686
+system-image-mips
+system-image-mipsel
+    od is buggy on mips[el]:
+    # echo Hello-hello-hello-hello | od -b
+    0000000 110 145 154 154 157 055 150 145 154 154 157 055 150 145 154 154
+    17767153361 157 055 150 145 154 154 157 012
+    0000000
+system-image-x86_64
+
+And these did not:
+system-image-armv6l  - hang on "Uncompressing Linux... done, booting the kernel"
+system-image-powerpc - hang early in kernel boot
+system-image-sparc   - hang early in userspace
+system-image-m68k    - my qemu doesn't like "-M q800"
+system-image-mips64  - init dies "Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000a"
+system-image-sh4     - qemu segfaults early in kernel boot