Update the default MACOSX_DEPLOYMENT_TARGET to 11.0

Makes the build script pass with defaults in usual developer environment.

Only the build on legacy systems should require fiddling with the settings
as it is a corner case.

ci/universal-build-macos.sh

@@ -14,7 +14,7 @@ set -x
 # OpenCPN needs to support even older macOS releases than the system
 # it is being built on, set MACOSX_DEPLOYMENT_TARGET environment
 # variable to use the respective SDK version.
-export MACOSX_DEPLOYMENT_TARGET=${MACOSX_DEPLOYMENT_TARGET:-10.13}
+export MACOSX_DEPLOYMENT_TARGET=${MACOSX_DEPLOYMENT_TARGET:-11.0}
 
 # URL of the repository to download the dependency bundle from
 export DEPS_BUNDLE_REPO="${DEPS_BUNDLE_REPO:-https://dl.cloudsmith.io/public/nohal/opencpn-dependencies/raw/files}"