Avoid parallel GCC install in build-many-glibcs.py.

A recent build-many-glibcs.py build
<https://sourceware.org/ml/libc-testresults/2017-q1/msg00067.html> ran
into what proves to be an old known bug
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42980> with parallel
install of GCC (one which as discussed there might require automake
changes to fix).  This patch makes build-many-glibcs.py avoid such
intermittent failures from parallel install by using -j1 for GCC make
install (the code in question also applies to binutils make install,
but it doesn't seem worth trying to avoid -j1 there; the builds and
installs of different toolchains are still fully parallel with each
other, this is only about the case when there are few enough of those
that multiple jobs can get used within a single make install).

	* scripts/build-many-glibcs.py (Config.build_cross_tool): Use -j1
	for make install.

2 files changed, 16 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index c9a6d804db..9961dc420e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-18  Joseph Myers  <joseph@codesourcery.com>
+
+	* scripts/build-many-glibcs.py (Config.build_cross_tool): Use -j1
+	for make install.
+
 2017-01-18  Siddhesh Poyarekar  <siddhesh@sourceware.org>
 
 	* po/bg.po: Merge from Translation Project.
diff --git a/scripts/build-many-glibcs.py b/scripts/build-many-glibcs.py
index d27e70b8bd..d2947e676b 100755
--- a/scripts/build-many-glibcs.py
+++ b/scripts/build-many-glibcs.py
@@ -1173,7 +1173,17 @@ class Config(object):
             cfg_cmd.extend(extra_opts)
         cmdlist.add_command('configure', cfg_cmd)
         cmdlist.add_command('build', ['make'])
-        cmdlist.add_command('install', ['make', 'install'])
+        # Parallel "make install" for GCC has race conditions that can
+        # cause it to fail; see
+        # <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42980>.  Such
+        # problems are not known for binutils, but doing the
+        # installation in parallel within a particular toolchain build
+        # (as opposed to installation of one toolchain from
+        # build-many-glibcs.py running in parallel to the installation
+        # of other toolchains being built) is not known to be
+        # significantly beneficial, so it is simplest just to disable
+        # parallel install for cross tools here.
+        cmdlist.add_command('install', ['make', '-j1', 'install'])
         cmdlist.cleanup_dir()
         cmdlist.pop_subdesc()