[Temp] Revert "Enable -Zfunction-sections by default for *-windows-{gnu,cygwin}"

This reverts commit e23a5fc.

Author: wesleywiser

compiler/rustc_target/src/spec/base/cygwin.rs

@@ -26,6 +26,8 @@ pub(crate) fn opts() -> TargetOptions {
     TargetOptions {
         os: "cygwin".into(),
         vendor: "pc".into(),
+        // FIXME(#13846) this should be enabled for cygwin
+        function_sections: false,
         linker: Some("gcc".into()),
         dynamic_linking: true,
         dll_prefix: "".into(),

compiler/rustc_target/src/spec/base/windows_gnu.rs

@@ -80,6 +80,8 @@ pub(crate) fn opts() -> TargetOptions {
         os: "windows".into(),
         env: "gnu".into(),
         vendor: "pc".into(),
+        // FIXME(#13846) this should be enabled for windows
+        function_sections: false,
         linker: Some("gcc".into()),
         dynamic_linking: true,
         dll_tls_export: false,