The existing behavior of using the build directory as the working
directory is useful if you want to move/copy the output directory around
and SRCDIR still refers the the source. But, it's more useful to have
the source directory be the working directory. Tools like cpp(__FILE__)
and other debug prints embed relative paths from the working directory.
We also have tools that expect the working directory to be $TOP.

Change-Id: Ia0f1d3c6b7df72d61cf5628efa2baa98bd19775b

Using a path with a space to execute soong is unlikely, but it
might as well work.  Quote all the paths in the soong scripts.

Soong and blueprint will still both fail if the relative path between
the soong script and the source directory has a space in it, but this
is even more unlikely.

Change-Id: I8986f10115209d69b09b82ffea26e4b10d29c197

bootstrap.bash creates a soong script in the output directory using
build/soong/soong.in.  This requires a manual rebootstrap any time
soong.in changes.  Instead, have bootstrap.bash symlink
build/soong/soong.bash to soong in the output directory, and create
a file called .soong.bootstrap in the output directory that contains
the variables that bootstrap.bash sets.

Change-Id: I5e6e54c2e8bdde876941e2e082f9ba177c757cbf