Including the case of building from tarball source.

When building from the tarball source, we ignore the
automatic download of submodules since they don't include
Git and submodules are already included.

Author: LuuuXXX

config.example.toml

@@ -48,7 +48,8 @@ change-id = 116881
 # We also currently only support this when building LLVM for the build triple.
 #
 # Set this to `"if-unchanged"` to only download if the llvm-project have not 
-# been modified. (if no changes, the logic is the same as `"if-available"`)
+# been modified. (If there are no changes or if built from tarball source, 
+# the logic is the same as "if-available")
 #
 # Note that many of the LLVM options are not currently supported for
 # downloading. Currently only the "assertions" option can be toggled.

src/bootstrap/src/core/build_steps/setup.rs

@@ -147,8 +147,14 @@ impl Step for Profile {
     }
 
     fn run(self, builder: &Builder<'_>) {
-        if self == Profile::Codegen {
-            builder.update_submodule(&Path::new("src/llvm-project"));
+        // During ./x.py setup once you select the codegen profile.
+        // The submodule will be downloaded. It does not work in the
+        // tarball case since they don't include Git and submodules
+        // are already included.
+        if !builder.rust_info().is_from_tarball() {
+            if self == Profile::Codegen {
+                builder.update_submodule(&Path::new("src/llvm-project"));
+            }
         }
         setup(&builder.build.config, self)
     }

src/bootstrap/src/core/config/config.rs

@@ -2108,12 +2108,16 @@ impl Config {
                 llvm::is_ci_llvm_available(&self, asserts)
             }
             Some(StringOrBool::String(s)) if s == "if-unchanged" => {
-                if self
-                    .last_modified_commit(&["src/llvm-project"], "download-ci-llvm", true)
-                    .is_none()
-                {
-                    // there are some untracked changes in the the given paths.
-                    false
+                if !self.rust_info.is_from_tarball() {
+                    if self
+                        .last_modified_commit(&["src/llvm-project"], "download-ci-llvm", true)
+                        .is_none()
+                    {
+                        // there are some untracked changes in the the given paths.
+                        false
+                    } else {
+                        llvm::is_ci_llvm_available(&self, asserts)
+                    }
                 } else {
                     llvm::is_ci_llvm_available(&self, asserts)
                 }