gas * write.c (maybe_generate_build_notes): Generate notes on a
per-code-section basis. Skip linkonce sections.
ld * testsuite/ld-elf/notes.exp: New file: Run new test.
* testsuite/ld-elf/note1_1.s: New file: Source file for test.
* testsuite/ld-elf/note1_2.s: New file: Source file for test.
* testsuite/ld-elf/note1.r: New file: Expected readelf output.
