fix(nemo-speech-cpp): support CMake 4

Homebrew CMake 4 rejects the old policy floor in the pinned SentencePiece helper. Select the oldest supported policy floor for the Darwin dependency build.

Assisted-by: Codex:gpt-5.6 [Codex CLI]

Author: localai-org-maint-bot

backend/go/nemo-speech-cpp/Makefile

@@ -280,12 +280,15 @@ itn: $(ITN_MARKER)
 
 $(SENTENCEPIECE_MARKER): | sources/NeMo-Speech.cpp
 	# Upstream's license copies use GNU install's -D flag, which BSD install
-	# does not support. Create the one missing directory and use the portable
-	# spelling before running the otherwise platform-independent script.
+	# does not support. Homebrew CMake 4 also rejects SentencePiece's old policy
+	# floor. Patch both incompatibilities before running the helper on Darwin.
 	@if [ "$(shell uname -s)" = Darwin ]; then \
 		cd sources/NeMo-Speech.cpp && \
 		mkdir -p .deps/sentencepiece/share/licenses/nemo-speech/third_party/sentencepiece && \
-		perl -pi -e 's/install -Dm0644/install -m 0644/g' scripts/build_sentencepiece_static.sh; \
+		perl -pi \
+			-e 's/install -Dm0644/install -m 0644/g;' \
+			-e 's/-DCMAKE_BUILD_TYPE=Release /-DCMAKE_BUILD_TYPE=Release -DCMAKE_POLICY_VERSION_MINIMUM=3.5 /;' \
+			scripts/build_sentencepiece_static.sh; \
 	fi
 	cd sources/NeMo-Speech.cpp && JOBS=$(JOBS) scripts/build_sentencepiece_static.sh