update to use go install instead of go get

go get: installing executables with 'go get' in module mode is
deprecated.
Use 'go install pkg@version' instead.
For more information, see
https://golang.org/doc/go-get-install-deprecation or run 'go help get'
or 'go help install'

Signed-off-by: Carlos Panato <ctadeu@gmail.com>

images/build/cross/default/Dockerfile

@@ -103,8 +103,8 @@ RUN mkdir $TMPDIR \
   && chmod o+t $TMPDIR
 
 # Get the code coverage tool and goimports
-RUN go get golang.org/x/tools/cmd/cover \
-           golang.org/x/tools/cmd/goimports \
+RUN go install golang.org/x/tools/cmd/cover@latest \
+    golang.org/x/tools/cmd/goimports@@latest \
     && go clean -cache
 
 # Cleanup a bit