Rollup merge of rust-lang#43312 - lu-zero:master, r=alexcrichton

powerpc: Ignore the stack-probes test

One little step further to have the test working fine on power8 :)

Author: Mark-Simulacrum

src/test/codegen/stack-probes.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // ignore-arm
+// ignore-powerpc
 // ignore-wasm
 // ignore-emscripten
 // ignore-windows