Rollup merge of rust-lang#38623 - alexcrichton:less-osx-warnings, r=aturon

std: Remove unused objects from compiler-builtins

We don't actually use trampoline_setup.c and all the `*tf3` business
seems related to f80/f128 business. Specifically this'll fix some
warnings showing up during builds on OSX.

Author: steveklabnik

src/libcompiler_builtins/build.rs

@@ -192,14 +192,12 @@ fn main() {
 
     if !target.contains("ios") {
         sources.extend(&["absvti2.c",
-                         "addtf3.c",
                          "addvti3.c",
                          "ashlti3.c",
                          "ashrti3.c",
                          "clzti2.c",
                          "cmpti2.c",
                          "ctzti2.c",
-                         "divtf3.c",
                          "divti3.c",
                          "ffsti2.c",
                          "fixdfti.c",
@@ -216,17 +214,13 @@ fn main() {
                          "floatuntixf.c",
                          "lshrti3.c",
                          "modti3.c",
-                         "multf3.c",
                          "multi3.c",
                          "mulvti3.c",
                          "negti2.c",
                          "negvti2.c",
                          "parityti2.c",
                          "popcountti2.c",
-                         "powitf2.c",
-                         "subtf3.c",
                          "subvti3.c",
-                         "trampoline_setup.c",
                          "ucmpti2.c",
                          "udivmodti4.c",
                          "udivti3.c",