build: Change native clang build to a normal stamps target

This will help in refactoring the target recipes.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Compile debug and release llvm and tools in separate directories

This will help refactor the target recipes.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Introduce a pattern rule for compilation targets

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: cosmetics: Place recipes in consistent debug before release order

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: cosmetics: Reorder KLEE build dependencies for consistency

Signed-off-by: Diego Biurrun <diego@biurrun.de>
Updated authors list

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>