ci: Install ninja and meson for toolchain build on macOS

This commit updates the CI workflow to install ninja and meson, which
are required for building the picolibc, for the toolchain build job on
macOS.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

.github/workflows/ci.yml

@@ -489,7 +489,7 @@ jobs:
         # (self-hosted runners are expected to provide all required dependencies)
         if [[ "${{ matrix.host.runner }}" =~ ^macos.* ]]; then
           brew install autoconf automake bash binutils boost coreutils gawk \
-                       gnu-sed gnu-tar help2man ncurses pkg-config
+                       gnu-sed gnu-tar help2man meson ncurses ninja pkg-config
         fi
 
         # Install dependencies for cross compilation