test-includes: Build a library instead of a binary

[imp]

Summary

We need to build the .o's, but don't need to link. Build a static
library instead of a binary to accmoplish this. This removes the need to
have all the libc and crt stuff built, which is required for a
binary. In addition, trying to build a non-standard binary runs into
trouble with undefined symbols on arm related to EABI, even when using a
simplified startup with -nostdlib -e start.

[jrtc27]

MIPS, being the usual odd one out, used __start not _start, FWIW...

Maybe best to be explicit with -e?

[jrtc27]

Alternatively you could build either a shared library or just the .o (/ a static library) and avoid the mild hackery needed to not get linker errors for the executable

[imp]

-e _start to future proof

[imp]

In D33452#756283, @jrtc27 wrote:

Alternatively you could build either a shared library or just the .o (/ a static library) and avoid the mild hackery needed to not get linker errors for the executable

I thought of that too... Years ago, I might have opted for the library, but libraries are becoming increasingly complex and I worry that it would be more fragile that -e, which seems a tiny bit more robust...

[markj]

tools/build/test-includes/test-includes.c

1

Is this comment really accurate now that the entry point is specified in the linker flags?

[imp]

Rework the comment to be correct, per markj

[imp]

hmmm, this fails on arm.

[imp]

build library

[imp]

Turns out brooks was right in a comment he left on the other review.
arm failed with the previous method, move to build a library method and see if that works.