Rollup merge of rust-lang#85807 - glaubitz:powerpc-disable-initial-exec-tls, r=Mark-Simulacrum

bootstrap: Disable initial-exec TLS model on powerpc

Fixes rust-lang#81334.

Author: JohnTitor

src/bootstrap/builder.rs

@@ -1291,7 +1291,7 @@ impl<'a> Builder<'a> {
         // efficient initial-exec TLS model. This doesn't work with `dlopen`,
         // so we can't use it by default in general, but we can use it for tools
         // and our own internal libraries.
-        if !mode.must_support_dlopen() {
+        if !mode.must_support_dlopen() && !target.triple.starts_with("powerpc-") {
             rustflags.arg("-Ztls-model=initial-exec");
         }