scan-build.bbclass: Do not depend on clang-native
scan-build.bbclass: Do not depend on clang-native

- Dependency on clang-native causes circular dependency
- Use spaces instead of tabs in shell functions
- Convert do_configure_prepend into a prefunc, makes it work
  with non-shell do_configure
- Use TARGET_CC_ARCH instead of HOST_CC_ARCH

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang