Try tweaking awk command

libcxx/test/libcxx/transitive_includes.gen.py

@@ -93,7 +93,7 @@
 // RUN: mkdir %t
 // RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} --trace-includes -fshow-skipped-includes --preprocess > /dev/null 2> %t/trace-includes.txt
 // RUN: %{{python}} %{{libcxx-dir}}/test/libcxx/transitive_includes_to_csv.py %t/trace-includes.txt > %t/actual_transitive_includes.csv
-// RUN: cat %{{libcxx-dir}}/test/libcxx/transitive_includes/%{{cxx_std}}.csv | awk '/^{escaped_header} / {{ print }}' > %t/expected_transitive_includes.csv
+// RUN: cat %{{libcxx-dir}}/test/libcxx/transitive_includes/%{{cxx_std}}.csv | awk '/^{escaped_header}[[:space:]]/ {{ print }}' > %t/expected_transitive_includes.csv
 // RUN: diff -w %t/expected_transitive_includes.csv %t/actual_transitive_includes.csv
 #include <{header}>
 """