mingw-w64: Many `run-make-fulldeps` tests fail due to some change in library search

[petrochenkov]

This is a regression from the last 1-2 weeks.
Not sure who is the right person to ping, @alexcrichton @michaelwoerister maybe.

Failing tests:

[run-make] run-make-fulldeps\a-b-a-linker-guard
[run-make] run-make-fulldeps\c-dynamic-dylib
[run-make] run-make-fulldeps\c-static-dylib
[run-make] run-make-fulldeps\dylib-chain
[run-make] run-make-fulldeps\extern-fn-reachable
[run-make] run-make-fulldeps\issue-15460
[run-make] run-make-fulldeps\issue-19371
[run-make] run-make-fulldeps\mixing-deps
[run-make] run-make-fulldeps\prefer-dylib
[run-make] run-make-fulldeps\simple-dylib
[run-make] run-make-fulldeps\static-nobundle

Typical failure looks like

---- [run-make] run-make-fulldeps\c-dynamic-dylib stdout ----

error: make failed
status: exit code: 2
command: "make"
stdout:
------------------------------------------
gcc.exe -ffunction-sections -fdata-sections -m64 -c -o /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/libcfoo.o cfoo.c
gcc.exe -ffunction-sections -fdata-sections -m64 -o /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/cfoo.dll /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/libcfoo.o -shared
PATH="/home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu:C:/msys64/home/we/rust/build\x86_64-pc-windows-gnu\stage2\bin:/home/we/rust/build/x86_64-pc-windows-gnu/stage0-tools/x86_64-pc-windows-gnu/release/deps:/home/we/rust/build/x86_64-pc-windows-gnu/stage0-sysroot/lib/rustlib/x86_64-pc-windows-gnu/lib:/mingw64/bin:/c/Users/we/.cargo/bin:/c/Program Files/CMake/bin:/c/Program Files/Git/cmd:/c/mingw-w64/x86_64-7.2.0-posix-seh-rt_v5-rev1/mingw64/bin:/c/ProgramData/chocolatey/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/usr/bin:/c/Windows/System32:/c/Windows:/c/Windows/System32/Wbem:/c/Windows/System32/WindowsPowerShell/v1.0:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl" 'C:/msys64/home/we/rust/build\x86_64-pc-windows-gnu\stage2\bin\rustc.exe' --out-dir /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu -L /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu  foo.rs -C prefer-dynamic
PATH="/home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu:C:/msys64/home/we/rust/build\x86_64-pc-windows-gnu\stage2\bin:/home/we/rust/build/x86_64-pc-windows-gnu/stage0-tools/x86_64-pc-windows-gnu/release/deps:/home/we/rust/build/x86_64-pc-windows-gnu/stage0-sysroot/lib/rustlib/x86_64-pc-windows-gnu/lib:/mingw64/bin:/c/Users/we/.cargo/bin:/c/Program Files/CMake/bin:/c/Program Files/Git/cmd:/c/mingw-w64/x86_64-7.2.0-posix-seh-rt_v5-rev1/mingw64/bin:/c/ProgramData/chocolatey/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/usr/bin:/c/Windows/System32:/c/Windows:/c/Windows/System32/Wbem:/c/Windows/System32/WindowsPowerShell/v1.0:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl" 'C:/msys64/home/we/rust/build\x86_64-pc-windows-gnu\stage2\bin\rustc.exe' --out-dir /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu -L /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu  bar.rs
PATH="/home/we/rust/build/x86_64-pc-windows-gnu/stage0-tools/x86_64-pc-windows-gnu/release/deps:/home/we/rust/build/x86_64-pc-windows-gnu/stage0-sysroot/lib/rustlib/x86_64-pc-windows-gnu/lib:/mingw64/bin:/c/Users/we/.cargo/bin:/c/Program Files/CMake/bin:/c/Program Files/Git/cmd:/c/mingw-w64/x86_64-7.2.0-posix-seh-rt_v5-rev1/mingw64/bin:/c/ProgramData/chocolatey/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/usr/bin:/c/Windows/System32:/c/Windows:/c/Windows/System32/Wbem:/c/Windows/System32/WindowsPowerShell/v1.0:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:C:/msys64/home/we/rust/build\x86_64-pc-windows-gnu\stage2\lib\rustlib\x86_64-pc-windows-gnu\lib" /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/bar
rm /home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/libcfoo.o

------------------------------------------
stderr:
------------------------------------------
C:/msys64/home/we/rust/build/x86_64-pc-windows-gnu/test/run-make-fulldeps/c-dynamic-dylib.stage2-x86_64-pc-windows-gnu/bar.exe: error while loading shared libraries: foo.dll: cannot open shared object file: No such file or directory
make: *** [Makefile:11: all] Error 127

------------------------------------------

[michaelwoerister]

Hm, I don't really know what could cause this.

[alexcrichton]

Sorry I'm not sure either :(

[nikomatsakis]

@petrochenkov if you can readily reproduce, can you try https://github.com/rust-lang-nursery/cargo-bisect-rustc ?

[pnkfelix]

triage: P-high

[petrochenkov]

@nikomatsakis
I'll try to bisect/investigate this weekend.

[petrochenkov]

So the offending commit is 84b5b34 (cc @Mark-Simulacrum )

As a result of that commit RustBuild.build_dir -> BUILD_DIR -> config.out -> ... -> TARGET_RPATH_DIR turn (in my case) from C:\msys64\home\we\rust\build into C:/msys64/home/we/rust/build (Python's getcwd behaves differently from previously used Rust's env::current_dir).
As a result PATH for run-make-fulldeps tests becomes broken and doesn't contain correct library directories.

We need to "normalize" separators for this path at some point, either at the beginning or in the end.