Reduce command length in regen-ulps.

I found that "make regen-ulps" failed when building with unmodified
GNU make 4.1, and an objdir /some/where/math/ longer than about 37
characters, because the list of tests in the "for run in $^" loop
exceeded the Linux kernel's MAX_ARG_STRLEN limit (131072 bytes) on the
length of a single argument passed to a command.

Some GNU/Linux distributions have a patch to make to work around this
limit (see e.g. Debian bug 688601), but clearly this ought to work
without needing such a patch.  This patch arranges for the shell loop
to be over the test names without a $(objdir) prefix, which reduces
the space used to less than half MAX_ARG_STRLEN.

(I think we ought to aim to get rid of bits/mathinline.h completely -
filing GCC bugs for any optimizations GCC can't currently do with
-ffast-math - which would mean we could halve the number of libm tests
run because separate inline function tests would no longer be needed.
However, with a long directory name even half the number of tests
could make this command exceed MAX_ARG_STRLEN without my patch.)

Tested regen-ulps on a system where it failed before this patch.

	* math/Makefile (run-regen-ulps): Add $(objpfx) to test name here.
	(regen-ulps): Use $(libm-tests) not $^ in shell loop.

1 files changed, 5 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index d8afa344b6..60c75f4178 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-01-02  Joseph Myers  <joseph@codesourcery.com>
+
+	* math/Makefile (run-regen-ulps): Add $(objpfx) to test name here.
+	(regen-ulps): Use $(libm-tests) not $^ in shell loop.
+
 2018-01-02  Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>
 
 	* NEWS: Add cosf and sincosf to list of optimized functions.