From a12c4dbf12f5dff559abc4464b905842031696da Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sun, 28 Jul 2024 09:53:13 -0400
Subject: build: De-duplicate conditionally-supported flags

---
 build/flags-if.sh | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/build/flags-if.sh b/build/flags-if.sh
index 098b2d3..7de7bbd 100755
--- a/build/flags-if.sh
+++ b/build/flags-if.sh
@@ -7,10 +7,18 @@
 
 set -eu
 
-FLAGS=$(sed -n '\|^///|{s|^/// ||; s|[^=]*= ||; p}' "$1")
+OLD_FLAGS="$XCC $XCPPFLAGS $XCFLAGS $XLDFLAGS $XLDLIBS"
+NEW_FLAGS=$(sed -n '\|^///|{s|^/// ||; s|[^=]*= ||; p}' "$1")
+build/cc.sh "$@" $NEW_FLAGS || exit 1
 
-if build/cc.sh "$@" $FLAGS; then
-    sed -n 's|^/// \(.*=.*\)|\1|p' "$1"
-else
-    exit 1
-fi
+# De-duplicate against the existing flags
+while IFS="" read -r line; do
+    case "$line" in
+        ///*=*)
+            flag="${line#*= }"
+            if [ "${OLD_FLAGS#*"$flag"}" = "$OLD_FLAGS" ]; then
+                printf '%s\n' "${line#/// }"
+            fi
+            ;;
+    esac
+done <"$1"
-- 
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