diff -ruN gcc-9.2.0-orig/libstdc++-v3/include/Makefile.in gcc-9.2.0/libstdc++-v3/include/Makefile.in
--- gcc-9.2.0-orig/libstdc++-v3/include/Makefile.in	2019-03-21 18:48:49.000000000 -0500
+++ gcc-9.2.0/libstdc++-v3/include/Makefile.in	2019-09-29 18:46:26.000000000 -0500
@@ -1875,6 +1875,8 @@
 @GLIBCXX_HOSTED_TRUE@install-data-local: install-headers
 @GLIBCXX_HOSTED_FALSE@install-data-local: install-freestanding-headers
 
+.NOTPARALLEL: install-headers
+
 # This is a subset of the full install-headers rule.  We only need <ciso646>,
 # <cstddef>, <cfloat>, <limits>, <climits>, <version>, <cstdint>, <cstdlib>,
 # <new>, <typeinfo>, <exception>, <initializer_list>, <cstdalign>, <cstdarg>,