Disabling jemalloc on the rust compiler builds for ARM.

petevine pointed out an issue that causes segfaults when the code is compiled on ARM using the current compilers with jemalloc. rust-lang/rust#30919

Author: warricksothr

scripts/build/build-rust.sh

@@ -174,6 +174,7 @@ cd build
 # Override the LLVM build targets. only need arm.
 ../configure \
   $CHANNEL \
+  --disable-jemalloc \
   --disable-valgrind \
   --enable-ccache \
   $CLANG_PARAMS \