build: Fix dependencies for start and asm files

Add a feature to enforce an explicit target file for assembler sources.
Add a build start file node list and use it as a test program
dependency.

The fix for #3846 and #4080 needs to be combined, because the fix
for #3846 requires the removal of 'before=["cstlib"]'. This patch fixes
two issues:

1. The tracking of start file dependencies.

2. Reflect that executables depend on the start files.

We need a start.o file in the right path so that the linker can find is
as specified by the linker script, and not for example a start.S.17.o
file in some path. This part is addressed by the "explicit_asm_target"
feature.

This build process extension

@after("apply_link")
@feature("cprogram", "cxxprogram")
def process_start_files(self):
    if getattr(self, "start_files", False):
        self.link_task.dep_nodes.extend(self.bld.start_files)

addresses 2.

Close #3846.
Close #4080.

0 files changed, 0 insertions, 0 deletions