[missing -fPIC] libstd fails to link on ARM with -flto

[MagaTailor]

Using gcc 4.9 and lto on armv7 leads to libstd's link failure:

/usr/bin/ld.bfd.real: error: /tmp/cczYIjMC.ltrans0.ltrans.o: requires unsupported dynamic reloc R_ARM_THM_MOVW_ABS_NC; recompile with -fPIC

error: linking with `cc` failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-L" "/tmp/rustc-nightly/arm-unknown-linux-gnueabihf/stage0/lib/rustlib/arm-unknown-linux-gnueabihf/lib" "arm-unknown-linux-gnueabihf/stage0/lib/rustlib/arm-unknown-linux-gnueabihf/lib/std-ca1c970e.0.o" "-o" "arm-unknown-linux-gnueabihf/stage0/lib/rustlib/arm-unknown-linux-gnueabihf/lib/libstd-ca1c970e.so" "arm-unknown-linux-gnueabihf/stage0/lib/rustlib/arm-unknown-linux-gnueabihf/lib/std-ca1c970e.metadata.o" "-Wl,-O1" "-nodefaultlibs" "-L" "arm-unknown-linux-gnueabihf/rt" "-L" "/usr/lib/llvm-3.6/lib" "-L" "/tmp/rustc-nightly/arm-unknown-linux-gnueabihf/stage0/lib/rustlib/arm-unknown-linux-gnueabihf/lib" "-Wl,-Bstatic" "-Wl,--whole-archive" "-l" "backtrace" "-Wl,--no-whole-archive" "-Wl,-Bdynamic" "-l" "dl" "-l" "pthread" "-l" "gcc_s" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/libcollections-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/liballoc-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/librustc_unicode-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/liballoc_jemalloc-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/liblibc-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/librand-ca1c970e.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "/tmp/rustc.K1iwqkGsmEEU/libcore-ca1c970e.rlib" "-Wl,--no-whole-archive" "-l" "pthread" "-l" "c" "-l" "m" "-l" "rt" "-shared" "-l" "compiler-rt"

Andrew Pinski from gcc suggested adding -fPIC to the linker's command line which ultimately helped.

[MagaTailor]

gchp/termbox-sys#16

[MagaTailor]

Adding -C link-args=-fPIC to RUSTFLAGS is enough to fix the issue. Strange that it still persists, though.

The size of the lib directory presently goes down from 180MB to 163MB thanks to -flto.