Revert "Delete .a file before writing static library."
Revert "Delete .a file before writing static library."

This reverts commit 3b035e041769424136a4e52cff457ec764623bda.

Reason for revert: Build-Win-Clang-arm64-Release-Android runs on
                   Windows and uses llvm-ar.

Original change's description:
> Delete .a file before writing static library.
> 
> The ar utility only adds symbols. As a result removed symbols are
> sometimes still present in later builds, leading to great confusion.
> Delete the .a file before recreating it with ar.
> 
> This is similar to what Chromium currently does in gcc_toolchain.gni.
> 
> Bug: skia:10363
> Change-Id: I133deb6da570ca38a539b4f0bb486b61d6a664bf
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295217
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

TBR=mtklein@google.com,53965154ffeecc4a10886eab9259e95965f2979a@google.com

Change-Id: I02ba93ce26eedb2b2362e96d2ebfcacbfb8e0902
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:10363
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295445
Reviewed-by: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia