Rollup merge of #39774 - frewsxcv:no-rustbuild, r=alexcrichton

Remove '--disable-rustbuild' option from configure script.

Fixes #39762.

Author: frewsxcv

configure

@@ -644,7 +644,6 @@ opt stage0-landing-pads 1 "enable landing pads during bootstrap with stage0"
 opt dist-host-only 0 "only install bins for the host architecture"
 opt inject-std-version 1 "inject the current compiler version of libstd into programs"
 opt llvm-version-check 1 "check if the LLVM version is supported, build anyway"
-opt rustbuild 1 "use the rust and cargo based build system"
 opt codegen-tests 1 "run the src/test/codegen tests"
 opt option-checking 1 "complain about unrecognized options in this configure script"
 opt ninja 0 "build LLVM using the Ninja generator (for MSVC, requires building in the correct environment)"