Stabilize linker-flavor flag.

This commit moves the linker-flavor flag from a debugging option to a
codegen option, thus stabilizing it. There are no feature flags
associated with this flag.

src/doc/rustc/src/codegen-options/index.md

@@ -22,6 +22,13 @@ This flag lets you append a single extra argument to the linker invocation.
 This flag lets you append multiple extra arguments to the linker invocation. The
 options should be separated by spaces.
 
+## linker-flavor
+
+This flag lets you control the linker flavor used by `rustc`. If a linker is given with the
+`-C linker` flag described above then the linker flavor is inferred from the value provided. If no
+linker is given then the linker flavor is used to determine the linker to use. Every `rustc` target
+defaults to some linker flavor.
+
 ## link-dead-code
 
 Normally, the linker will remove dead code. This flag disables this behavior.

src/librustc/session/config.rs

@@ -1136,6 +1136,8 @@ options! {CodegenOptions, CodegenSetter, basic_codegen_options,
         "enable incremental compilation"),
     default_linker_libraries: Option<bool> = (None, parse_opt_bool, [UNTRACKED],
         "allow the linker to link its default libraries"),
+    linker_flavor: Option<LinkerFlavor> = (None, parse_linker_flavor, [UNTRACKED],
+                                           "Linker flavor"),
 }
 
 options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
@@ -1292,8 +1294,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "pass `-install_name @rpath/...` to the macOS linker"),
     sanitizer: Option<Sanitizer> = (None, parse_sanitizer, [TRACKED],
                                     "Use a sanitizer"),
-    linker_flavor: Option<LinkerFlavor> = (None, parse_linker_flavor, [UNTRACKED],
-                                           "Linker flavor"),
     fuel: Option<(String, u64)> = (None, parse_optimization_fuel, [TRACKED],
         "set the optimization fuel quota for a crate"),
     print_fuel: Option<String> = (None, parse_opt_string, [TRACKED],

src/librustc_codegen_ssa/back/link.rs

@@ -192,11 +192,7 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
 
     // linker and linker flavor specified via command line have precedence over what the target
     // specification specifies
-    if let Some(ret) = infer_from(
-        sess,
-        sess.opts.cg.linker.clone(),
-        sess.opts.debugging_opts.linker_flavor,
-    ) {
+    if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
         return ret;
     }
 

src/test/compile-fail/issue-10755.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: -C linker=llllll -Z linker-flavor=ld
+// compile-flags: -C linker=llllll -C linker-flavor=ld
 // error-pattern: linker `llllll` not found
 
 fn main() {

src/test/compile-fail/nolink-with-link-args.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // error-pattern:aFdEfSeVEE
-// compile-flags: -Z linker-flavor=ld
+// compile-flags: -C linker-flavor=ld
 
 /* We're testing that link_args are indeed passed when nolink is specified.
 So we try to compile with junk link_args and make sure they are visible in