Add "file" command for Linux/ARM (and magic number file)

file/arm/Dockerfile

@@ -0,0 +1,8 @@
+FROM andrewd/musl-cross-arm
+MAINTAINER Andrew Dunham <andrew@du.nham.ca>
+
+# Add our build script
+ADD build.sh /build/build.sh
+
+# This builds the program and copies it to /output
+CMD /build/build.sh

file/arm/build.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+
+set -e
+set -o pipefail
+set -x
+
+
+FILE_VERSION=5.23
+
+# Set up path
+export PATH=$PATH:/opt/cross/arm-linux-musleabihf/bin/
+
+
+function build_file() {
+    cd /build
+
+    # Download
+    curl -LO ftp://ftp.astron.com/pub/file/file-${FILE_VERSION}.tar.gz
+    tar xzvf file-${FILE_VERSION}.tar.gz
+    cd file-${FILE_VERSION}
+
+    # Don't run tests.
+    printf "all:\n\ttrue\n\ninstall:\n\ttrue\n\n" > tests/Makefile.in
+
+    # Fix header files
+    sed -i 's/memory.h/string.h/' src/encoding.c src/ascmagic.c
+
+    # Firstly, compile natively.
+    ./configure --disable-shared
+    make -j4
+
+    # Copy the generated binary to our build dir
+    cp ./src/file /build/file
+
+    # Clean up
+    make distclean || true
+
+    # Configure for cross-compiling
+    CC='arm-linux-musleabihf-gcc -Wl,-static -static-libgcc -static -frandom-seed=build-file-arm -D_GNU_SOURCE -D_BSD_SOURCE' \
+        ./configure \
+            --disable-shared \
+            --host=$(arm-linux-musleabihf-gcc -dumpmachine | sed 's/musl/gnu/') \
+            --build=i686
+
+    # Use the native version of file to compile our magic file.
+    sed -i 's|FILE_COMPILE = file${EXEEXT}|FILE_COMPILE = /build/file|' ./magic/Makefile
+
+    # Build the cross-compiled version.
+    make
+    arm-linux-musleabihf-strip ./src/file
+}
+
+
+function doit() {
+    build_file
+
+    # Copy to output
+    if [ -d /output ]
+    then
+        OUT_DIR=/output/`uname | tr 'A-Z' 'a-z'`/arm
+        mkdir -p $OUT_DIR
+        cp /build/file-${FILE_VERSION}/src/file $OUT_DIR/
+        echo "** Finished **"
+    else
+        echo "** /output does not exist **"
+    fi
+}
+
+doit