Save .log output files to out/arch/

This is cleaner as it removes yet another .gitignore rule and allows
for one command per arch.

This was prompted by the recent Docker patch creating files as root,
which then breaks future host runs.

Also separate all arguments by newlines. This:

- makes it much easier to minimize when reporting QEMU bugs
- shows the full command on the screen despite line wrapping being turned off
  by one of the annoying emulators, to be investigated.

The commands are not yet pristine, because:

- there are some leading spaces
- options not sorted

but it is already a huge improvement, and those operations are now be easy from Vim.

The general strategy is:

- end every variable containing a command with a newline
- when expanding such variables, don't add an extra newline

README.adoc

@@ -1436,7 +1436,7 @@ To enable initrd instead of the default ext2 disk image, do:
 Notice how it boots fine, even though this leads to not giving QEMU the `-drive` option, as can be verified with:
 
 ....
-cat ./run.log
+cat ./out/x86_64/run.sh
 ....
 
 Also as expected, there is no filesystem persistency, since we are doing everything in memory:
@@ -3799,7 +3799,7 @@ Stdout shows a line with the full command of type:
 and this line is also saved to a file for convenience:
 
 ....
-cat ./run.log
+cat ./out/arm/run.sh
 ....
 
 Next, you will also want to give the relevant images to save them time. Zip the images with: