Update build.sh to skip testing Foundation for linux, which requires building SwiftPM from source first

Author: finagolfin

swift-ci/sdks/android/scripts/build.sh

@@ -447,7 +447,7 @@ for arch in $archs; do
             ${local_build} \
             --host-test \
             --skip-test-linux \
-            --skip-test-xctest \
+            --skip-test-xctest --skip-test-foundation \
             --build-swift-static-stdlib \
             --install-swift \
             --install-libdispatch \