add CI for mips-musl

and fix the statvfs struct for this target

.travis.yml

@@ -79,6 +79,9 @@ matrix:
     - os: linux
       env: TARGET=powerpc64-unknown-linux-gnu
       rust: stable
+    - os: linux
+      env: TARGET=mips-unknown-linux-musl
+      rust: stable
     - os: linux
       env: TARGET=mipsel-unknown-linux-musl
       rust: stable

ci/docker/mips-unknown-linux-musl/Dockerfile

@@ -0,0 +1,14 @@
+FROM ubuntu:16.04
+
+RUN apt-get update
+RUN apt-get install -y --no-install-recommends \
+        gcc libc6-dev qemu-user ca-certificates qemu-system-mips curl \
+        bzip2
+
+RUN mkdir /toolchain
+RUN curl -L https://downloads.openwrt.org/snapshots/trunk/ar71xx/generic/OpenWrt-SDK-ar71xx-generic_gcc-5.3.0_musl-1.1.15.Linux-x86_64.tar.bz2 | \
+      tar xjf - -C /toolchain --strip-components=2
+
+ENV PATH=$PATH:/rust/bin:/toolchain/bin \
+    CC_mips_unknown_linux_musl=mips-openwrt-linux-gcc \
+    CARGO_TARGET_MIPS_UNKNOWN_LINUX_MUSL_LINKER=mips-openwrt-linux-gcc

src/unix/notbsd/linux/mod.rs

@@ -126,9 +126,12 @@ s! {
         pub f_files: ::fsfilcnt_t,
         pub f_ffree: ::fsfilcnt_t,
         pub f_favail: ::fsfilcnt_t,
+        #[cfg(target_endian = "little")]
         pub f_fsid: ::c_ulong,
         #[cfg(target_pointer_width = "32")]
         pub __f_unused: ::c_int,
+        #[cfg(target_endian = "big")]
+        pub f_fsid: ::c_ulong,
         pub f_flag: ::c_ulong,
         pub f_namemax: ::c_ulong,
         __f_spare: [::c_int; 6],