Move class static variables to function static

Chrome bans use of static initializers. As a result we can't roll
libdexfile changes into Chromium.
This CL moves static class members DexFile::g_lock and
DexFile::g_mapped_dex_files into the static function
DexFile::CreateFromDisk(the only user of those
static class members).

Test:
  - Build `chrome/android:monochrome_static_initializers` successfully
    https://chromium.googlesource.com/chromium/src.git/+/HEAD/docs/static_initializers.md#step-1-use-objdump-to-report-them

Bug: 1365904
Change-Id: Ibfe96c18e1747c2483db0b2f0a39b4918c809298
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/third_party/libunwindstack/+/3942065
Reviewed-by: Tushar Agarwal <agarwaltushar@google.com>
Reviewed-by: Mike Wittman <wittman@chromium.org>
4 files changed