This integrates Jan Kratochvil's nice race reproducer from PR
testsuite/12649 into the testsuite infrustructure directly.
With this, one only has to do either 'make check-read1' or 'make check
READ1="1"' to preload the read1.so library into expect.
Currently only enabled for glibc/GNU systems, and if
build==host==target.
gdb/testsuite/ChangeLog:
* Makefile.in (EXTRA_RULES, CC): New variables, get from
configure.
(EXPECT): Handle READ1 being set.
(all): Depend on EXTRA_RULES.
(check-read1, expect-read1, read1.so, read1): New rules.
* README (Testsuite Parameters): Document the READ1 make variable.
(Race detection): New section.
* configure: Regenerate.
* configure.ac: If build==host==target, and running under a
GNU/glibc system, add read1 to the extra Makefile rules.
(EXTRA_RULES): AC_SUBST it.
* lib/read1.c: New file.
gdb/ChangeLog:
* Makefile.in (check-read1): New rule.
2a31c6236d