ci(macos): trust PX4 brew taps for Homebrew 6.0

Homebrew 6.0 (2026-06-11) makes tap-trust mandatory and refuses to load
formulae from untrusted third-party taps. This broke every macOS build:
brew install aborted with "Refusing to load formula px4/px4/fastdds from
untrusted tap px4/px4" before pouring any package, so ccache (and the
rest of the toolchain) was never installed and setup-ccache failed with
"ccache: command not found".

Trust the three required taps non-interactively before installing from
them. Guarded behind a brew trust capability check so older Homebrew,
which has no trust gate, skips it.

Signed-off-by: Ramon Roche <mrpollo@gmail.com>

Tools/setup/macos.sh

@@ -51,6 +51,18 @@ brew tap osx-cross/arm
 brew tap PX4/px4
 brew tap discoteq/discoteq
 
+# Homebrew 6.0+ refuses to load formulae from third-party taps unless they
+# are explicitly trusted ("Refusing to load formula ... from untrusted tap").
+# Trust each tap non-interactively before installing from it. Without this,
+# `brew install` aborts before pouring any package (including ccache).
+# `brew trust` only exists on Homebrew 6.0+; guard it so older versions,
+# which don't gate untrusted taps, skip it silently.
+if brew trust --help &> /dev/null; then
+	brew trust osx-cross/arm
+	brew trust PX4/px4
+	brew trust discoteq/discoteq
+fi
+
 # Package list. This replaces the px4-dev meta-formula, which is kept
 # as a deprecated no-op upstream. See PX4/homebrew-px4 for history.
 PX4_BREW_PACKAGES=(