[MacPorts] #56322: rust @1.25.0: buid failed on OS X <= 10.9

[MacPorts]

#56322: rust @1.25.0: buid failed on OS X <= 10.9
--------------------+----------------------
 Reporter:  l2dy    |      Owner:  g5pw
     Type:  defect  |     Status:  assigned
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:
 Keywords:          |       Port:  rust
--------------------+----------------------
 I updated `rust` to 1.25.0 and its llvm dependency to `llvm-6.0` in
 [77b2ac31e027672243e78942002737e7185ba125/macports-ports]. However build
 failed on OS X <= 10.9 on Buildbot with this error:

 {{{
 running: "/usr/bin/clang" "-O2" "-ffunction-sections" "-fdata-sections"
 "-fPIC" "-ffunction-sections" "-fdata-sections" "-fPIC" "--target=x86_64
 -apple-darwin" "-stdlib=libc++" "--target=x86_64-apple-darwin" "-fno-
 builtin" "-fvisibility=hidden" "-ffreestanding" "-fomit-frame-pointer"
 "-DVISIBILITY_HIDDEN" "-o"
 "/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.25.0-src/build/x86_64
 -apple-darwin/stage0-std/x86_64-apple-darwin/release/build
 /compiler_builtins-1d69f6fbd68a066f/out/../../libcompiler_builtins
 /compiler-rt/lib/builtins/x86_64/floatundidf.o" "-c"
 "../../libcompiler_builtins/compiler-rt/lib/builtins/x86_64/floatundidf.S"
 cargo:warning=../../libcompiler_builtins/compiler-
 rt/lib/builtins/x86_64/floatundidf.S:37:11: error: unexpected token in
 directive
 cargo:warning=.balign 4 .subsections_via_symbols ; .globl ___floatundidf ;
 ; .private_extern ___floatundidf ; ___floatundidf:
 cargo:warning=          ^
 exit code: 1
 }}}

 I've only tested it on 10.13 and didn't discover this issue. Sorry for
 pushing the update in a hurry.

-- 
Ticket URL: <https://trac.macports.org/ticket/56322>
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