build-sys: drop unused $RUNTIME_DIR
build-sys: allow update-hwdb with seperate build dir
systemd-analyze: reword comments
service: fixup after ifdef dropping

Commit 88516c0 removed one line too much.
systemd-analyze: pipe through SED_PROCESS

To be able to add --version and change python binary.
systemd-analyze: use specified binary, add --version

Python binary used in the she-bang line in installed
scripts can be set with ./configure PYTHON_BINARY=...
Defaults to the same path as python used during compilation.

Adding --version makes systemd-analyze behave consistently with the
rest of installed programs.

The lines in ./configure output are reordered to keep all yes/no lines
separate.  I think that this makes the output clearer.
build-sys: invoke scripts with $PYTHON during build

Python binary to be used during compilation can be set with
./configure PYTHON=...

The she-bang line is removed, since it is not used anymore.
build-sys: fix message about gintrospection

When gobject-introspection-devel was not available, the message
was missing the yes/no part