Revert "ci: target baseline instead of spacemit_x60 on riscv64-linux"

This reverts commit fa445d8.

Narrator: It did, in fact, make a difference.

For whatever reason, building LLVM against spacemit_x60 or baseline makes no
noticeable difference in terms of performance, but building the Zig compiler
against spacemit_x60 does. Also, the miscompilation that was causing
riscv64-linux-debug to fail was in the LLVM libraries, not in the Zig compiler,
so we may as well take the win here.

Author: alexrp

ci/riscv64-linux-debug.sh

@@ -7,7 +7,7 @@ set -e
 
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
-MCPU="baseline"
+MCPU="spacemit_x60"
 CACHE_BASENAME="zig+llvm+lld+clang-riscv64-linux-musl-0.15.0-dev.929+31e46be74"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"

ci/riscv64-linux-release.sh

@@ -7,7 +7,7 @@ set -e
 
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
-MCPU="baseline"
+MCPU="spacemit_x60"
 CACHE_BASENAME="zig+llvm+lld+clang-riscv64-linux-musl-0.15.0-dev.929+31e46be74"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"