Swap TargetOptions::linker_is_gnu default from false to true and update targets as appropriate.

compiler/rustc_target/src/spec/apple_base.rs

@@ -22,6 +22,7 @@ pub fn opts(os: &str) -> TargetOptions {
         // macOS has -dead_strip, which doesn't rely on function_sections
         function_sections: false,
         dynamic_linking: true,
+        linker_is_gnu: false,
         executables: true,
         families: vec!["unix".to_string()],
         is_like_osx: true,

compiler/rustc_target/src/spec/illumos_base.rs

@@ -33,6 +33,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         families: vec!["unix".to_string()],
         is_like_solaris: true,
+        linker_is_gnu: false,
         limit_rdylib_exports: false, // Linker doesn't support this
         eliminate_frame_pointer: false,
         eh_frame_header: false,

compiler/rustc_target/src/spec/l4re_base.rs

@@ -20,6 +20,7 @@ pub fn opts() -> TargetOptions {
         executables: true,
         panic_strategy: PanicStrategy::Abort,
         linker: Some("ld".to_string()),
+        linker_is_gnu: false,
         families: vec!["unix".to_string()],
         ..Default::default()
     }

compiler/rustc_target/src/spec/mod.rs

@@ -1086,7 +1086,7 @@ pub struct TargetOptions {
     /// Version of DWARF to use if not using the default.
     /// Useful because some platforms (osx, bsd) only want up to DWARF2.
     pub dwarf_version: Option<u32>,
-    /// Whether the linker support GNU-like arguments such as -O. Defaults to false.
+    /// Whether the linker support GNU-like arguments such as -O. Defaults to true.
     pub linker_is_gnu: bool,
     /// The MinGW toolchain has a known issue that prevents it from correctly
     /// handling COFF object files with more than 2<sup>15</sup> sections. Since each weak
@@ -1307,7 +1307,7 @@ impl Default for TargetOptions {
             is_like_fuchsia: false,
             is_like_wasm: false,
             dwarf_version: None,
-            linker_is_gnu: false,
+            linker_is_gnu: true,
             allows_weak_linkage: true,
             has_rpath: false,
             no_default_libraries: true,

compiler/rustc_target/src/spec/msvc_base.rs

@@ -16,6 +16,7 @@ pub fn opts() -> TargetOptions {
         is_like_windows: true,
         is_like_msvc: true,
         lld_flavor: LldFlavor::Link,
+        linker_is_gnu: false,
         pre_link_args,
         abi_return_struct_as_int: true,
         emit_debug_gdb_scripts: false,

compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs

@@ -14,6 +14,7 @@ pub fn target() -> Target {
             linker_flavor: LinkerFlavor::PtxLinker,
             // The linker can be installed from `crates.io`.
             linker: Some("rust-ptx-linker".to_string()),
+            linker_is_gnu: false,
 
             // With `ptx-linker` approach, it can be later overridden via link flags.
             cpu: "sm_30".to_string(),

compiler/rustc_target/src/spec/solaris_base.rs

@@ -8,6 +8,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         families: vec!["unix".to_string()],
         is_like_solaris: true,
+        linker_is_gnu: false,
         limit_rdylib_exports: false, // Linker doesn't support this
         eh_frame_header: false,