Bug 1320710 - Target i686 rust code on linux32. r=froydnj

Official Mozilla builds no longer support non-SSE2 x86 cpus,
so we can use the default i686 rust target here. This allows
better code generation and removes a dependency on the extra
i585 rust std library.

MozReview-Commit-ID: BHrm4tieIym

--HG--
extra : rebase_source : e791068b6128b9f3153b9c85ebd8551d583c2bc7

browser/config/tooltool-manifests/linux32/releng.manifest

@@ -17,8 +17,8 @@
 },
 {
 "version": "rustc 1.14.0-beta.2 (e627a2e6e 2016-11-16) repack",
-"size": 96275316,
-"digest": "26c11e34df81f5d7ffafc3492df9c6821f644a2e2eda5cfbbcdb1ac23e4ee196007b417c862c60a97bbf66e4be9c801400990938cd3aefec19b1cf9eaf1a9b54",
+"size": 94830820,
+"digest": "6f2a1cf325d957f0328d2d853fc07944a857e872f6e44df15f6ebb45c032c0ebbf52f56c872bc72927ebcdd830002d759dd92e8fc90048b52c07058955c69c4c",
 "algorithm": "sha512",
 "filename": "rustc.tar.xz",
 "unpack": true

build/moz.configure/rust.configure

@@ -122,7 +122,7 @@ def rust_triple_alias(host_or_target):
             # OpenBSD
             ('x86_64', 'OpenBSD'): 'x86_64-unknown-openbsd',
             # Linux
-            ('x86', 'Linux'): 'i586-unknown-linux-gnu',
+            ('x86', 'Linux'): 'i686-unknown-linux-gnu',
             # Linux
             ('x86_64', 'Linux'): 'x86_64-unknown-linux-gnu',
             # OS X and iOS