[Wallet] Fix iOS bundle script failing with our monorepo setup

The solutions found in react-native-community/cli#656 didn't help
but setting PROJECT_ROOT in the build phase script worked.

packages/mobile/ios/celo.xcodeproj/project.pbxproj

@@ -410,7 +410,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "# First set the path to sentry.properties\nexport SENTRY_PROPERTIES=sentry.properties\n\n# Setup nvm and set node\n[ -z \"$NVM_DIR\" ] && export NVM_DIR=\"$HOME/.nvm\"\n\nif [[ -s \"$HOME/.nvm/nvm.sh\" ]]; then\n. \"$HOME/.nvm/nvm.sh\"\nelif [[ -x \"$(command -v brew)\" && -s \"$(brew --prefix nvm)/nvm.sh\" ]]; then\n. \"$(brew --prefix nvm)/nvm.sh\"\nfi\n\n# Set up the nodenv node version manager if present\nif [[ -x \"$HOME/.nodenv/bin/nodenv\" ]]; then\neval \"$(\"$HOME/.nodenv/bin/nodenv\" init -)\"\nfi\n\n[ -z \"$NODE_BINARY\" ] && export NODE_BINARY=\"node\"\n\n$NODE_BINARY ../../../node_modules/@sentry/cli/bin/sentry-cli react-native xcode \\\n../../../node_modules/react-native/scripts/react-native-xcode.sh\n";
+			shellScript = "# First set the path to sentry.properties\nexport SENTRY_PROPERTIES=sentry.properties\n\n# Setup nvm and set node\n[ -z \"$NVM_DIR\" ] && export NVM_DIR=\"$HOME/.nvm\"\n\nif [[ -s \"$HOME/.nvm/nvm.sh\" ]]; then\n. \"$HOME/.nvm/nvm.sh\"\nelif [[ -x \"$(command -v brew)\" && -s \"$(brew --prefix nvm)/nvm.sh\" ]]; then\n. \"$(brew --prefix nvm)/nvm.sh\"\nfi\n\n# Set up the nodenv node version manager if present\nif [[ -x \"$HOME/.nodenv/bin/nodenv\" ]]; then\neval \"$(\"$HOME/.nodenv/bin/nodenv\" init -)\"\nfi\n\n[ -z \"$NODE_BINARY\" ] && export NODE_BINARY=\"node\"\n\n# Fixes bundling failing with our monorepo setup\nexport PROJECT_ROOT=\"$PROJECT_DIR/..\"\n\n$NODE_BINARY ../../../node_modules/@sentry/cli/bin/sentry-cli react-native xcode \\\n../../../node_modules/react-native/scripts/react-native-xcode.sh\n";
 		};
 		2D02E4CB1E0B4B27006451C7 /* Bundle React Native Code And Images */ = {
 			isa = PBXShellScriptBuildPhase;