Fix: ensure gomobile builds disable modules

- At this time, gomobile does not support modules.

- With Go 1.13.1, Mobile/iOS/build-psiphon-framework.sh
  fails without GO111MODULE=off.

MobileLibrary/Android/make.bash

@@ -10,6 +10,9 @@ fi
 # $1, if specified, is go build tags
 if [ -z ${1+x} ]; then BUILD_TAGS=""; else BUILD_TAGS="$1"; fi
 
+# At this time, gomobile doesn't support modules
+export GO111MODULE=off
+
 # Don't use '-u' to force updates because the docker builds always pull
 # the latest versions. Outside of Docker, be aware that these dependencies
 # will not be overridden w/ new versions if they already exist in $GOPATH

MobileLibrary/iOS/build-psiphon-framework.sh

@@ -7,6 +7,9 @@ if [ -z ${1+x} ]; then BUILD_TAGS=""; else BUILD_TAGS="$1"; fi
 # Modify this value as we use newer Go versions.
 GO_VERSION_REQUIRED="1.11.13"
 
+# At this time, gomobile doesn't support modules
+export GO111MODULE=off
+
 # Reset the PATH to macOS default. This is mainly so we don't execute the wrong
 # gomobile executable.
 PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/go/bin