Add quotes around paths in bash scripts

Follow up to crrev.com/c/2125626.

This allows depot_tools commands to run successfully when depot_tools is
installed in a path containing spaces.

Change-Id: I8f99dbdcb3b1acf27d51ce26b6153f643b8d4dcd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2127675
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
diff --git a/git-upstream-diff b/git-upstream-diff
index ba16876..08cad36 100755
--- a/git-upstream-diff
+++ b/git-upstream-diff
@@ -6,4 +6,4 @@
 # git_upstream_diff.py -- Provide the diff between the current branch and its
 # upstream.
 
-. $(type -P python_runner.sh)
+. "$(type -P python_runner.sh)"