Rollup merge of #80662 - rxrbln:master, r=estebank

Added support for i386-unknown-linux-gnu and i486-unknown-linux-gnu

Support for both can be useful when creating new firmware, boot loaders,
or embedded operating systems.

Author: Dylan-DPC

compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs

@@ -0,0 +1,8 @@
+use crate::spec::Target;
+
+pub fn target() -> Target {
+    let mut base = super::i686_unknown_linux_gnu::target();
+    base.cpu = "i386".to_string();
+    base.llvm_target = "i386-unknown-linux-gnu".to_string();
+    base
+}

compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs

@@ -0,0 +1,8 @@
+use crate::spec::Target;
+
+pub fn target() -> Target {
+    let mut base = super::i686_unknown_linux_gnu::target();
+    base.cpu = "i486".to_string();
+    base.llvm_target = "i486-unknown-linux-gnu".to_string();
+    base
+}