Pass the TMPDIR directly to the command when dumping makefile variables.

External applications such as metrics uploader depends on the TMPDIR.
DumpMakeVars is changing the TMPDIR environment variable value. Once
the work is done, TMPDIR directory is deleted. Additional flow of
the tool or external applications can panic since TMPDIR directory
does not exist. Since this is an isolated case, pass the TMPDIR
directory to the command of dumping the makefile variables.

Bug: b/140638454
Test: * Ran lunch command with ANDROID_ENABLE_METRICS_UPLOAD set
        and metrics_uploader did not crash.
      * m nothing
Change-Id: Ib78a3f8cfb5da48f65bd9bce1511e9abdf3d9cca