internal/rosa/cmake: use hardcoded build directory

This eliminates some nondeterminism. Still getting 3-stage non-determinism in runtimes and clang, though.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/cmake.go

@@ -109,7 +109,7 @@ chmod -R +w "${ROSA_CMAKE_SOURCE}"
 		"ROSA_CMAKE_SOURCE=" + sourcePath.Append(attr.Append...).String(),
 		"ROSA_INSTALL_PREFIX=/work" + prefix.String(),
 	}, attr.Env), scriptEarly+`
-cd "$(mktemp -d)"
+mkdir /cure && cd /cure
 cmake -G Ninja \
 	-DCMAKE_C_COMPILER_TARGET="${ROSA_TRIPLE}" \
 	-DCMAKE_CXX_COMPILER_TARGET="${ROSA_TRIPLE}" \