meson: Prefix each element of firmware path

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <20220624154042.51512-1-akihiko.odaki@gmail.com>
[Rewrite shell function without using Bash extensions. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
6 files changed