[gn build] Port a3ce29f

Author: aeubanks

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -664,6 +664,7 @@ if (current_toolchain == default_toolchain) {
       "__numeric/transform_exclusive_scan.h",
       "__numeric/transform_inclusive_scan.h",
       "__numeric/transform_reduce.h",
+      "__pstl/cpu_algos/cpu_traits.h",
       "__random/bernoulli_distribution.h",
       "__random/binomial_distribution.h",
       "__random/cauchy_distribution.h",