Fix build on Raspberry Pi2.

[Adenilson]

As the debian based linux distro uses 'alternatives' to allow selecting
tools (i.e. compiler), hardcoding the CC compiler to arm-linux-gnueabihf-gcc
may not point to the user selected default compiler.

[Adenilson]

Output of running vanilla:
pi@raspberrypi /media/iso/stuff/deps-servo/rust-png $ cargo build --release
Updating registry https://github.com/rust-lang/crates.io-index
Compiling png-sys v1.6.16 (file:///media/iso/stuff/deps-servo/rust-png)
Compiling gcc v0.3.8
Compiling libc v0.1.8
Build failed, waiting for other jobs to finish...
failed to run custom build command for png-sys v1.6.16 (file:///media/iso/stuff/deps-servo/rust-png)
Process didn't exit successfully: /media/iso/stuff/deps-servo/rust-png/target/release/build/png-sys-10e5e57738c3b96a/build-script-build (exit code: 101)
--- stdout
running: "/media/iso/stuff/deps-servo/rust-png/png-sys/libpng-1.6.16/configure" "--with-libpng-prefix=RUST_" "--host=arm-unknown-linux-gnueabihf"
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for arm-unknown-linux-gnueabihf-strip... no
checking for strip... strip
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... no
checking for mawk... mawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether to enable maintainer-specific portions of Makefiles... no
checking for arm-unknown-linux-gnueabihf-gcc... arm-unknown-linux-gnueabihf-gcc
checking whether the C compiler works... no

--- stderr
configure: error: in `/media/iso/stuff/deps-servo/rust-png/target/release/build/png-sys-10e5e57738c3b96a/out':
configure: error: C compiler cannot create executables

[metajack]

As is, I believe this patch breaks android, whose target triple is arm-linux-androideabi. @mmatyas might have better suggestions on how to solve this too.

[Adenilson]

Added the change where it will test for: gnueabihf.

[mmatyas]

I'm going to try this on my board, will report back.

[Adenilson]

Any feedback on this?

[mmatyas]

Sorry, my board is a tiny bit slow, took several hours to build the latest rust and servo. I have a weird configuration error right now, even if I apply this patch, modify or even delete build.rs, my changes don't get used at all. I've double checked my paths, so I'm not really sure how this happened.

Anyway, this issue probably affects most dependencies, so I'll apply the other ARM patches and see how many of them fail. Again, sorry for the delay.

PS. The link in the comment section throws 404, it should be https://wiki.debian.org/DebianAlternatives, with an extra S at the end.

[Adenilson]

You don't need to compile servo & Inc to test this, just compile rust-png. :-)

And I faced the same error (i.e. pointing to wrong compiler) in libfreetype2 and rust-stb-image after the ARM specific patches.

I'm working on fixing those as we speak, but I would really like to get this landed ASAP.

[Adenilson]

If it helps, I can share the servo required rustc (i.e. specific hash) as it takes 8hs to compile it.

[mmatyas]

Ok, this patch works for me, for both on board and cross compile. As for the other patches, in most makefiles CC is set like CC := $(TARGET)-gcc, changing them to CC ?= $(TARGET)-gcc should work, and that would allow the users to override this setting.

[metajack]

@bors-servo r+

[metajack]

@bors-servo r+

[bors-servo]

📌 Commit 42c92c8 has been approved by metajack

[bors-servo]

⌛ Testing commit 42c92c8 with merge 1c8dacf...

[bors-servo]

☀️ Test successful - travis