When Swift imports C structs, it synthesizes an initializer that takes no arguments and zero-initializes the C struct.
When C++ interop is enabled, Clang treats all C structs as if they were C++ structs. This means that some of the C structs will get a default constructor implicitly generated by Clang. This implicit default constructor will not zero-initialize trivial fields of the struct.
This is a common source of confusion and subtle bugs for developers who try to enable C++ interop in existing projects that use C interop and rely on zero-initialization of C structs.
rdar://115909532
Also, make the analogous change to apple/swift-driver#1372, which gets the
sanitizer tests working on Android again, and remove the lld_lto feature in the
tests, which is now unused.
Also, make some related changes, like updating a path in the Android doc, making sure the
`unknown` vendor is always used, and using `CPU` instead of `CODEGENERATOR`.
`Swift` is the name of the Swift standard library module. Creating another module with this name breaks assumptions in the compiler and caused these two tests to fail.
