https://bugs.gentoo.org/868384
--- a/src/ksba-config.in
+++ b/src/ksba-config.in
@@ -126,7 +126,7 @@ if test "$echo_cflags" = "yes"; then
     fi
     tmp=""
     for i in $includes $cflags; do
-       if echo "$tmp" | fgrep -v -- "$i" >/dev/null; then
+       if echo "$tmp" | grep -F -v -- "$i" >/dev/null; then
            tmp="$tmp $i"
        fi
     done
@@ -140,7 +140,7 @@ if test "$echo_libs" = "yes"; then
     fi
     tmp=""
     for i in $libdirs $libs; do
-       if echo "$tmp" | fgrep -v -- "$i" >/dev/null; then
+       if echo "$tmp" | grep -F -v -- "$i" >/dev/null; then
            tmp="$tmp $i"
        fi
     done