Rollup merge of #1960 - JohnTitor:disable-sparc, r=JohnTitor

Disable `sparc-unknown-linux-gnu` for now

ci/build.sh

@@ -201,6 +201,8 @@ for TARGET in $TARGETS; do
     fi
 done
 
+# Disable the below because of LLVM on `compiler_builtins` 0.1.36:
+# sparc-unknown-linux-gnu
 RUST_LINUX_NO_CORE_TARGETS="\
 aarch64-pc-windows-msvc \
 aarch64-unknown-cloudabi \
@@ -241,7 +243,6 @@ riscv32imc-unknown-none-elf \
 riscv32gc-unknown-linux-gnu \
 riscv64gc-unknown-none-elf \
 riscv64imac-unknown-none-elf \
-sparc-unknown-linux-gnu \
 sparc64-unknown-netbsd \
 
 thumbv6m-none-eabi \