go : run `go mod tidy` before building examples + fix permissions (#296)

* run `go mod tidy` before building examples

Running `make examples` after cloning the repository gives the following
error:

```
...
[100%] Built target whisper
gmake[3]: Leaving directory '/tmp/exp/whisper.cpp/bindings/go/build'
gmake[2]: Leaving directory '/tmp/exp/whisper.cpp/bindings/go/build'
gmake[1]: Leaving directory '/tmp/exp/whisper.cpp/bindings/go/build'
Build example go-model-download
Build example go-whisper
examples/go-whisper/process.go:11:2: missing go.sum entry for module providing package github.com/go-audio/wav (imported by github.com/ggerganov/whisper.cpp/bindings/go/examples/go-whisper); to add:
        go get github.com/ggerganov/whisper.cpp/bindings/go/examples/go-whisper
make: *** [Makefile:26: examples/go-whisper] Error 1
```

* remove executable bit from various files

bindings/go/Makefile

@@ -11,8 +11,7 @@ whisper: mkdir
 	@${CMAKE} -S ../.. -B ${BUILD_DIR} -D BUILD_SHARED_LIBS=off -D WHISPER_NO_AVX2=on
 	@${CMAKE} --build ${BUILD_DIR} --target whisper
 
-test: model-small whisper
-	@go mod tidy
+test: model-small whisper modtidy
 	@go test -v .
 	@go test -v ./pkg/whisper/...
 
@@ -21,7 +20,7 @@ examples: $(EXAMPLES_DIR)
 model-small: mkdir examples/go-model-download
 	@${BUILD_DIR}/go-model-download -out models small.en
 
-$(EXAMPLES_DIR): mkdir whisper 
+$(EXAMPLES_DIR): mkdir whisper modtidy
 	@echo Build example $(notdir $@)
 	@go build ${BUILD_FLAGS} -o ${BUILD_DIR}/$(notdir $@) ./$@
 
@@ -31,8 +30,10 @@ mkdir:
 	@echo Mkdir ${MODELS_DIR}
 	@install -d ${MODELS_DIR}
 
+modtidy:
+	@go mod tidy
+
 clean: 
 	@echo Clean
 	@rm -fr $(BUILD_DIR)
-	@go mod tidy
 	@go clean