Fix get_os and get_arch

get_os and get_arch were failing to return a value in the error
case; they were also assuming that strings are indexed from 1. No
idea how they ever worked, but anyway, fixed.

Author: catamorphism

src/comp/driver/rustc.rs

@@ -166,26 +166,31 @@ options:
 }
 
 fn get_os(str triple) -> session::os {
-    if (_str::find(triple, "win32") > 0 ||
-        _str::find(triple, "mingw32") > 0 ) {
+    if (_str::find(triple, "win32") >= 0 ||
+        _str::find(triple, "mingw32") >= 0 ) {
         ret session::os_win32;
-    } else if (_str::find(triple, "darwin") > 0) { ret session::os_macos; }
-    else if (_str::find(triple, "linux") > 0) { ret session::os_linux; }
+    } else if (_str::find(triple, "darwin") >= 0) { ret session::os_macos; }
+    else if (_str::find(triple, "linux") >= 0) { ret session::os_linux; }
+    else { log_err "Unknown operating system!"; fail; }
 }
 
 fn get_arch(str triple) -> session::arch {
-    if (_str::find(triple, "i386") > 0 ||
-        _str::find(triple, "i486") > 0 ||
-        _str::find(triple, "i586") > 0 ||
-        _str::find(triple, "i686") > 0 ||
-        _str::find(triple, "i786") > 0 ) {
+    if (_str::find(triple, "i386") >= 0 ||
+        _str::find(triple, "i486") >= 0 ||
+        _str::find(triple, "i586") >= 0 ||
+        _str::find(triple, "i686") >= 0 ||
+        _str::find(triple, "i786") >= 0 ) {
         ret session::arch_x86;
-    } else if (_str::find(triple, "x86_64") > 0) {
+    } else if (_str::find(triple, "x86_64") >= 0) {
         ret session::arch_x64;
-    } else if (_str::find(triple, "arm") > 0 ||
-        _str::find(triple, "xscale") > 0 ) {
+    } else if (_str::find(triple, "arm") >= 0 ||
+        _str::find(triple, "xscale") >= 0 ) {
         ret session::arch_arm;
     }
+    else {
+        log_err ("Unknown architecture! " + triple);
+        fail;
+    }
 }
 
 fn get_default_sysroot(str binary) -> str {