gcc-wrapper: comment on alternate setup hook

We now have an alternate setup hook for gcc-wrapper that uses -I to add
include paths rather than -isystem. The latter flag can change the
search order specified by the build system. For KDE 5 packages, we don't
want that!

1 files changed, 6 insertions, 0 deletions

diff --git a/pkgs/build-support/gcc-wrapper/setup-hook-stdinc.sh b/pkgs/build-support/gcc-wrapper/setup-hook-stdinc.sh
index b6a6673575bb..22e778b06904 100644
--- a/pkgs/build-support/gcc-wrapper/setup-hook-stdinc.sh
+++ b/pkgs/build-support/gcc-wrapper/setup-hook-stdinc.sh
@@ -1,3 +1,9 @@
+# This is an alternate setup hook for gcc-wrapper that uses the -I flag to
+# add include search paths instead of -isystem. We need this for some packages
+# because -isystem can change the search order specified by prior -I flags.
+# Changing the search order can point gcc to the wrong package's headers.
+# The -I flag will never change the order of prior flags.
+
 export NIX_CC=@out@
 
 addCVars () {