How Build Cache for React Native works: caching the C++ your CI keeps recompiling
A React Native build is really two builds stacked on top of each other. On Android, Gradle compiles your Kotlin and Java, then drops down into cmake and ndk-build to compile the C++ that ships inside Hermes, Folly, ReactCommon, and your own turbo modules. On iOS, Xcode does the equivalent: Swift and Objective-C on top, the same C++ underneath via Clang. Two build systems, two languages on top, one shared set of C++ underneath.