Patch to use pkg-config during ngx_brotli's auto-discovery. Requires pkg-config to be configured properly (e.g. through PKG_CONFIG_PATH) before nginx's configure script is executed.

ngx_brotli-pkgconfig-auto-discovery.patch

--- a/config
+++ b/config
@@ -66,8 +66,8 @@ ngx_feature_test="BrotliEncoderCreateInstance(NULL, NULL, NULL)"

 # auto-discovery
 ngx_feature="Brotli library"
-ngx_feature_path=
-ngx_feature_libs="-lbrotlienc -lm"
+ngx_feature_path="$(pkg-config --cflags-only-I libbrotlienc | sed 's/-I//g')"
+ngx_feature_libs="$(pkg-config --libs libbrotlienc)"
 . auto/feature

 if [ $ngx_found = no ]; then
@@ -116,8 +116,8 @@ if [ $ngx_found = no ]; then

     # auto-discovery
     ngx_feature="Brotli library"
-    ngx_feature_path=
-    ngx_feature_libs="-lbrotlienc -lm"
+    ngx_feature_path="$(pkg-config --cflags-only-I libbrotlienc | sed 's/-I//g')"
+    ngx_feature_libs="$(pkg-config --libs libbrotlienc)"
     . auto/feature
 fi