Cross compiling fails

[candrews]

I'm running an amd64 system trying to cross compile for x86 (which is common for multilib).

Building quiche by running:
cargo build --target=i686-unknown-linux-gnu

results in this build failure:

   Compiling quiche v0.1.0 (/var/tmp/portage/net-libs/quiche-0.1.0/work/quiche-0.1.0-abi_x86_32.x86)
error: failed to run custom build command for `quiche v0.1.0 (/var/tmp/portage/net-libs/quiche-0.1.0/work/quiche-0.1.0-abi_x86_32.x86)`

Caused by:
  process didn't exit successfully: `/var/tmp/portage/net-libs/quiche-0.1.0/work/quiche-0.1.0-abi_x86_32.x86/target/release/build/quiche-0b547c5a4bcd114c/build-script-build` (exit code: 101)
--- stdout
running: "cmake" "/var/tmp/portage/net-libs/quiche-0.1.0/work/quiche-0.1.0-abi_x86_32.x86/deps/boringssl" "-DCMAKE_INSTALL_PREFIX=/var/tmp/portage/net-libs/quiche-0.1.0/work/quiche-0.1.0-abi_x86_32.x86/target/i686-unknown-linux-gnu/release/build/quiche-f20871fc80c099ad/out" "-DCMAKE_C_FLAGS= -ffunction-sections -fdata-sections -fPIC -m32 -march=i686 -march=native -pipe -fuse-linker-plugin -flto -ftree-vectorize -ftree-slp-vectorize -falign-functions=32 -fgraphite-identity -floop-nest-optimize -fno-lto -fno-use-linker-plugin" "-DCMAKE_C_COMPILER=/usr/lib/ccache/bin/x86_64-pc-linux-gnu-gcc" "-DCMAKE_CXX_FLAGS= -ffunction-sections -fdata-sections -fPIC -m32 -march=i686 -march=native -pipe -fuse-linker-plugin -flto -ftree-vectorize -ftree-slp-vectorize -falign-functions=32 -fgraphite-identity -floop-nest-optimize -fno-lto -fno-use-linker-plugin" "-DCMAKE_CXX_COMPILER=/usr/lib/ccache/bin/x86_64-pc-linux-gnu-g++" "-DCMAKE_BUILD_TYPE=RelWithDebInfo"

[snip]

/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(aesni-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(aes-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(ghash-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(md5-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(sha1-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(sha256-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(sha512-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(vpaes-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(x86_64-mont.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(chacha-x86_64.S.o)' is incompatible with i386 output
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: i386:x86-64 architecture of input file `../crypto/libcrypto.a(x86_64-mont5.S.o)' is incompatible with i386 output

Here's the full build log:
net-libs:quiche-0.1.0:20191127-222131.log

Regardless of the --target provided to cargo, quiche is always building boringssl for the native arch, not the target one.

Parameters need to be provided to the boringssl cmake build process so it builds for the cargo provided --target arch and not the native arch.

[candrews]

rust-lang/cmake-rs#80 seems relevant.

[junhochoi]

@candrews I made a PR #285 to fix this issue. Let me know this works for you.