[glibc/google/grte/v5-2.27/master] Work around a make 3.81 segfault with clang

[glibc/google/grte/v5-2.27/master] Work around a make 3.81 segfault with clang

[Fangrui Song]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4d4222dd27ca5be9d0d16ab180b98cc65cf7e5e3

commit 4d4222dd27ca5be9d0d16ab180b98cc65cf7e5e3
Author: Stan Shebs <stanshebs@google.com>
Date:   Fri Jun 1 14:57:50 2018 -0700

    Work around a make 3.81 segfault with clang

Diff:
---
 elf/Makefile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/elf/Makefile b/elf/Makefile
index 7ce0925072..b9ea53932a 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -455,10 +455,12 @@ $(objpfx)librtld.map: $(objpfx)dl-allobjs.os $(common-objpfx)libc_pic.a
 	mv -f $@T $@
 
 # For lld, add to regexp below for optional address and size to be at front of line.
+# Also, Google b/79865038 reports that make 3.81 can segfault while iterating over
+# the repeated lib+file entries in the map; work around with sort -u .
 $(objpfx)librtld.mk: $(objpfx)librtld.map Makefile
 	LC_ALL=C \
 	sed -n 's@^[0-9a-f ]*$(common-objpfx)\([^(]*\)(\([^)]*\.os\)) *.*$$@\1 \2@p' \
-	    $< | \
+	    $< | LC_ALL=C sort -u | \
 	while read lib file; do \
 	  case $$lib in \
 	  libc_pic.a) \