buildx: inconsistency between tc.find and tc.cacheFile calls

[Meroje]

Hi, we found that when using the setup-buildx action the toolcache would never be used and buildx is always downloaded.

It looks like the find call is done with an explicit arch param that is actually built as {platform}-{arch}

actions-toolkit/src/buildx/install.ts

Line 51 in 417136d

toolPath = tc.find('buildx', fversion, this.platform());

However later when copying to the toolcache there is no override done of the arch param which results in the @actions sdk defaulting to os.arch https://github.com/actions/toolkit/blob/457303960f03375db6f033e214b9f90d79c3fe5c/packages/tool-cache/src/tool-cache.ts#L465