link failure on nightly, windows

[matthiaskrgr]

Since rustc 1.42.0-nightly (01a46509a 2019-12-20) I'm getting link failures on travis ci that did not occur previously (rustc 1.42.0-nightly (0de96d37f 2019-12-19))
https://travis-ci.org/matthiaskrgr/cargo-cache/jobs/628012845#L195

  = note: C:\Users\travis\build\matthiaskrgr\cargo-cache\target\debug\deps\liblibgit2_sys-b28d7af61e5f6f84.rlib(cache.o): In function `printf':
          C:/ProgramData/chocolatey/lib/mingw/tools/install/mingw64/x86_64-w64-mingw32/include/stdio.h:349: undefined reference to `__imp___acrt_iob_func'
          C:\Users\travis\build\matthiaskrgr\cargo-cache\target\debug\deps\liblibgit2_sys-b28d7af61e5f6f84.rlib(diff_print.o): In function `git_diff_print_callback__to_file_handle':
          C:\Users\travis\.cargo\registry\src\github.com-1ecc6299db9ec823\libgit2-sys-0.10.0/libgit2/src/diff_print.c:744: undefined reference to `__imp___acrt_iob_func'
          C:\Users\travis\build\matthiaskrgr\cargo-cache\target\debug\deps\liblibgit2_sys-b28d7af61e5f6f84.rlib(xdiffi.o): In function `xdl_bug':
          C:\Users\travis\.cargo\registry\src\github.com-1ecc6299db9ec823\libgit2-sys-0.10.0/libgit2/src/xdiff/xdiffi.c:816: undefined reference to `__imp___acrt_iob_func'
          C:\Users\travis\build\matthiaskrgr\cargo-cache\target\debug\deps\liblibgit2_sys-b28d7af61e5f6f84.rlib(util.o): In function `printf':
          C:/ProgramData/chocolatey/lib/mingw/tools/install/mingw64/x86_64-w64-mingw32/include/stdio.h:349: undefined reference to `__imp___acrt_iob_func'

I'm wondering if this is related to #67020

Edit: travis config can be found here: https://github.com/matthiaskrgr/cargo-cache/blob/master/.travis.yml#L15

[Mark-Simulacrum]

cc @michaelwoerister @pnkfelix

Given our desire to keep nightly working over the holidays if we confirm it is indeed this PR and do not have a fix in the pipeline I will work on reverting it today/tomorrow.

[Mark-Simulacrum]

@matthiaskrgr informs me that this appears only broken on Travis, and one of the symbols in the log is repeatedly mentioned in #47048 which leads me to suspect that it's a change in the environment rather than a bug on our side, so I withdraw my eagerness to revert at least until we have more information.

[mati865]

I also think something has changed in Travis environment or dependencies. Can you try running old nightly in the Travis?

[Mark-Simulacrum]

Oh, I forgot to make a note here. @matthiaskrgr confirmed on Discord that both nightlies (today's and yesterday's) fail on Travis with the current travis environment, so something changed there. This is then not strictly a bug on our side (or at least is a duplicate of #47048 I expect), so closing.

[kpcyrd]

It seems travis also broken stable rust on windows: https://travis-ci.org/kpcyrd/sn0int/jobs/628652634