Pin cc version

Author: clubby789

compiler/rustc_llvm/Cargo.toml

@@ -9,6 +9,10 @@ libc = "0.2.73"
 # tidy-alphabetical-end
 
 [build-dependencies]
+# FIXME: updating cc past 1.0.79 breaks libstd bootstrapping, pin
+# to the last working version here so `cargo update` doesn't cause the
+# a higher version to be selected
+# https://github.com/rust-lang/cc-rs/issues/913
 # tidy-alphabetical-start
-cc = "1.0.69"
+cc = "=1.0.79"
 # tidy-alphabetical-end