We aren't interested in bundled Brotli.

Use pkg-config to detect Brotli's install path.

--- a/config
+++ b/config
@@ -59,93 +59,19 @@ have=NGX_HTTP_BROTLI_STATIC_MODULE . auto/have  # deprecated
 ngx_module_type=HTTP_FILTER
 ngx_module_name=ngx_http_brotli_filter_module
 
-brotli="/usr/local"
+brotli=$(pkg-config --variable=prefix libbrotlienc)
 
 if [ ! -f "$brotli/include/brotli/encode.h" ]; then
 
-brotli="$ngx_addon_dir/deps/brotli/c"
-
-if [ ! -f "$brotli/include/brotli/encode.h" ]; then
 cat << END
 
 $0: error: \
-Brotli library is missing from the $brotli directory.
-
-Please make sure that the git submodule has been checked out:
-
-    cd $ngx_addon_dir && git submodule update --init && cd $PWD
+Brotli library not found. Don't you have app-arch/brotli installed?
 
 END
     exit 1
 fi
 
-ngx_module_incs="$brotli/include"
-ngx_module_deps="$brotli/common/constants.h \
-                 $brotli/common/dictionary.h \
-                 $brotli/common/version.h \
-                 $brotli/enc/backward_references.h \
-                 $brotli/enc/backward_references_hq.h \
-                 $brotli/enc/backward_references_inc.h \
-                 $brotli/enc/bit_cost.h \
-                 $brotli/enc/bit_cost_inc.h \
-                 $brotli/enc/block_encoder_inc.h \
-                 $brotli/enc/block_splitter.h \
-                 $brotli/enc/block_splitter_inc.h \
-                 $brotli/enc/brotli_bit_stream.h \
-                 $brotli/enc/cluster.h \
-                 $brotli/enc/cluster_inc.h \
-                 $brotli/enc/command.h \
-                 $brotli/enc/compress_fragment.h \
-                 $brotli/enc/compress_fragment_two_pass.h \
-                 $brotli/enc/context.h \
-                 $brotli/enc/dictionary_hash.h \
-                 $brotli/enc/entropy_encode.h \
-                 $brotli/enc/entropy_encode_static.h \
-                 $brotli/enc/fast_log.h \
-                 $brotli/enc/find_match_length.h \
-                 $brotli/enc/hash.h \
-                 $brotli/enc/hash_forgetful_chain_inc.h \
-                 $brotli/enc/hash_longest_match64_inc.h \
-                 $brotli/enc/hash_longest_match_inc.h \
-                 $brotli/enc/hash_longest_match_quickly_inc.h \
-                 $brotli/enc/hash_to_binary_tree_inc.h \
-                 $brotli/enc/histogram.h \
-                 $brotli/enc/histogram_inc.h \
-                 $brotli/enc/literal_cost.h \
-                 $brotli/enc/memory.h \
-                 $brotli/enc/metablock.h \
-                 $brotli/enc/metablock_inc.h \
-                 $brotli/enc/port.h \
-                 $brotli/enc/prefix.h \
-                 $brotli/enc/quality.h \
-                 $brotli/enc/ringbuffer.h \
-                 $brotli/enc/static_dict.h \
-                 $brotli/enc/static_dict_lut.h \
-                 $brotli/enc/utf8_util.h \
-                 $brotli/enc/write_bits.h"
-ngx_module_srcs="$brotli/common/dictionary.c \
-                 $brotli/enc/backward_references.c \
-                 $brotli/enc/backward_references_hq.c \
-                 $brotli/enc/bit_cost.c \
-                 $brotli/enc/block_splitter.c \
-                 $brotli/enc/brotli_bit_stream.c \
-                 $brotli/enc/cluster.c \
-                 $brotli/enc/compress_fragment.c \
-                 $brotli/enc/compress_fragment_two_pass.c \
-                 $brotli/enc/dictionary_hash.c \
-                 $brotli/enc/encode.c \
-                 $brotli/enc/entropy_encode.c \
-                 $brotli/enc/histogram.c \
-                 $brotli/enc/literal_cost.c \
-                 $brotli/enc/memory.c \
-                 $brotli/enc/metablock.c \
-                 $brotli/enc/static_dict.c \
-                 $brotli/enc/utf8_util.c \
-                 $ngx_addon_dir/src/ngx_http_brotli_filter_module.c"
-ngx_module_libs="-lm"
-
-else # encode.h in /usr/local
-
 ngx_module_incs="$brotli/include"
 ngx_module_deps="$brotli/include/brotli/encode.h \
                  $brotli/include/brotli/port.h \
@@ -153,8 +79,6 @@ ngx_module_deps="$brotli/include/brotli/encode.h \
 ngx_module_srcs="$ngx_addon_dir/src/ngx_http_brotli_filter_module.c"
 ngx_module_libs="-lbrotlienc -lm"
 
-fi # encode.h in /usr/local
-
 ngx_module_order="$ngx_module_name \
                   ngx_pagespeed \
                   ngx_http_postpone_filter_module \