ci: add Dockerfiles for uclibc on armv7 and mipsel

Author: skrap

ci/docker/armv7-unknown-linux-uclibceabihf/Dockerfile

@@ -0,0 +1,17 @@
+FROM ubuntu:20.04
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        gcc libc6-dev qemu-user ca-certificates qemu-system-arm curl \
+        xz-utils patch
+
+RUN mkdir /toolchain
+
+RUN curl --retry 5 -L https://toolchains.bootlin.com/downloads/releases/toolchains/armv7-eabihf/tarballs/armv7-eabihf--uclibc--bleeding-edge-2020.08-1.tar.bz2 | \
+    tar xjf - -C /toolchain --strip-components=1
+RUN /toolchain/relocate-sdk.sh
+
+ENV PATH=$PATH:/rust/bin:/toolchain/bin \
+    STAGING_DIR=/toolchain/armv7-buildroot-linux-uclibceabihf/sysroot \
+    CC_armv7_unknown_linux_uclibc=armv7-buildroot-linux-uclibc-gcc \
+    CARGO_TARGET_ARMV7_UNKNOWN_LINUX_UCLIBCEABIHF_LINKER=armv7-buildroot-linux-uclibc-gcc \
+    CARGO_TARGET_ARMV7_UNKNOWN_LINUX_UCLIBCEABIHF_RUNNER="qemu-arm -L /toolchain/arm-buildroot-linux-uclibcgnueabihf/sysroot/"

ci/docker/mipsel-unknown-linux-uclibc/Dockerfile

@@ -0,0 +1,22 @@
+FROM ubuntu:20.04
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        gcc libc6-dev qemu-user ca-certificates qemu-system-mipsel curl \
+        xz-utils patch
+
+RUN mkdir /toolchain
+
+# binutils	2.33.1
+# gcc	9.3.0
+# gdb	8.3.1
+# linux-headers	4.9.234
+# uclibc	1.0.34
+RUN curl --retry 5 -L https://toolchains.bootlin.com/downloads/releases/toolchains/mips32el/tarballs/mips32el--uclibc--stable-2020.08-1.tar.bz2 | \
+    tar xjf - -C /toolchain --strip-components=1
+RUN /toolchain/relocate-sdk.sh
+
+ENV PATH=$PATH:/rust/bin:/toolchain/bin \
+    STAGING_DIR=/toolchain/mipsel-buildroot-linux-uclibc/sysroot \
+    CC_mipsel_unknown_linux_uclibc=mipsel-buildroot-linux-uclibc-gcc \
+    CARGO_TARGET_MIPSEL_UNKNOWN_LINUX_UCLIBC_LINKER=mipsel-buildroot-linux-uclibc-gcc \
+    CARGO_TARGET_MIPSEL_UNKNOWN_LINUX_UCLIBC_RUNNER="qemu-mipsel -L /toolchain/mipsel-buildroot-linux-uclibc/sysroot/"