Reliably track proc macro & build.rs code coverage

[ryoqun]

Problem

Coverages for proc-macro and build.rs isn't reliable because these are executed at the compile-time, which can result in being skipped due to caches.

• several build.rs files incorrectly disappear even for this nano PR (+4 −5 changes) (https://codecov.io/gh/solana-labs/solana/pull/8199/changes, Fix nightly clippy warnings #8199 (comment))

> # [Codecov](https://codecov.io/gh/solana-labs/solana/pull/8199?src=pr&el=h1) Report
> 
> > Merging [#8199](https://codecov.io/gh/solana-labs/solana/pull/8199?src=pr&el=desc) into [master](https://codecov.io/gh/solana-labs/solana/commit/df782b93ae2c4196567340d9f6425b3cfc314fdc?src=pr&el=desc) will **decrease** coverage by `<.1%`.
> > The diff coverage is `0%`.
> 
> ```diff
> @@           Coverage Diff            @@
> ##           master   #8199     +/-   ##
> ========================================
> - Coverage    81.3%   81.3%   -0.1%     
> ========================================
>   Files         251     248      -3     
>   Lines       53962   53933     -29     
> ========================================
> - Hits        43876   43852     -24     
> + Misses      10086   10081      -5
> ```

And, I'm obsessed just with coverages too much; But this is the final PR of my several-month-long journey to the perfect coverage tracking. After this, there should be no coverage issues whatsoever!!!

Summary of Changes

Disable caching for them by touch-ing. Yes, build time will get slower but coverage job isn't longest to finish. :p Also, the number of affected solana-* crates are small compared to vast of other dependant crates.

And, I'm relieved from unreliable coverages finally.

Background

In anticipation of #8012 (which introduces both moderate amount of proc macro and build.rs, which would disturbance other PRs after merged without this.)

[codecov]

Codecov Report

Merging #8210 into master will increase coverage by <.1%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #8210     +/-   ##
========================================
+ Coverage    81.3%   81.3%   +<.1%     
========================================
  Files         251     251             
  Lines       54039   54039             
========================================
+ Hits        43955   43956      +1     
+ Misses      10084   10083      -1

[ryoqun]

@mvines Thanks for quick approval! :)