Bump rust nightly to 2020-07-12

[mvines]

No description provided.

[mvines]

Hmm, coverage build fails with errors like:

 undefined reference to `sol_log_'

[Aaron1011]

The undefined reference to 'sol_log_' error is due to the fact that pre-1.2.10 versions of solana-sdk require sol_log_ to be provided by solana-sdk-bpf-test. Since solana-sdk doesn't actually declare a dependency on solana-sdk-bpf-test, rustc is not guaranteed to pass the rlib archives to the linker in the proper order (solana-sdk before solana-sdk-bpf-test).

The coverage build passes -C link-dead-code, which causes the sol_log wrapper (which references sol_log_ to be codegenned), even if is never called. If the rlibs happen to get passed to the linker in the wrong order, a link error will occur.

[Aaron1011]

@mvines You should be able to bump spl-memo now

[codecov]

Codecov Report

Merging #11015 into master will decrease coverage by 0.0%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #11015     +/-   ##
=========================================
- Coverage    82.2%    82.1%   -0.1%     
=========================================
  Files         318      318             
  Lines       73249    73275     +26     
=========================================
- Hits        60218    60201     -17     
- Misses      13031    13074     +43