std: Don't let rust_panic get inlined

[alexcrichton]

It's meant for breakpoints, so if it gets inlined we can't set a
breakpoint on it easily!

Will hopefully help fix at least one aspect of #49013

[rust-highfive]

r? @dtolnay

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[dtolnay]

@bors r+

[bors]

📌 Commit 243030b has been approved by dtolnay

[bors]

⌛ Testing commit 243030b with merge 02c2f0d54d78d591237e14ecde03aa51a28adfef...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job dist-x86_64-musl of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:07d840fa:start=1538161892939494988,finish=1538161892944842095,duration=5347107
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:22c8d5ee
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:0bb440d5
travis_time:start:0bb440d5
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:06e7a45e
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[alexcrichton]

@bors: retry

[bors]

⌛ Testing commit 243030b with merge 9653f79...

[kennytm]

@bors retry r- Wrongly rescheduled.