build: Remove llvm-instr-asan from list of directories to generate

The corresponding rule was deleted some time ago.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Introduce consistent naming scheme for asan compile targets

This will help in refactoring the target recipes.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Refactor list of QEMU directories into a variable

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Split klee debug and release targets

This will help in refactoring the target recipes and allows
building KLEE with different options in the same build tree.

It also makes sure that the right CXXFLAGS are passed to debug
KLEE builds.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
build: Refactor order-only configure directory dependency with a pattern

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