cmake: add support for brotli

Currently CMake cannot detect Brotli support. This adds detection of the
libraries and associated header files. It also adds this to the
generated config.

Closes #2392

CMake/FindBrotli.cmake

@@ -0,0 +1,20 @@
+include(FindPackageHandleStandardArgs)
+
+find_path(BROTLI_INCLUDE_DIR "brotli/decode.h")
+
+find_library(BROTLICOMMON_LIBRARY NAMES brotlicommon)
+find_library(BROTLIDEC_LIBRARY NAMES brotlidec)
+
+find_package_handle_standard_args(BROTLI
+    FOUND_VAR
+      BROTLI_FOUND
+    REQUIRED_VARS
+      BROTLIDEC_LIBRARY
+      BROTLICOMMON_LIBRARY
+      BROTLI_INCLUDE_DIR
+    FAIL_MESSAGE
+      "Could NOT find BROTLI"
+)
+
+set(BROTLI_INCLUDE_DIRS ${BROTLI_INCLUDE_DIR})
+set(BROTLI_LIBRARIES ${BROTLICOMMON_LIBRARY} ${BROTLIDEC_LIBRARY})

CMakeLists.txt

@@ -521,6 +521,18 @@ if(CURL_ZLIB)
   endif()
 endif()
 
+option(CURL_BROTLI "Set to ON to enable building curl with brotli support." OFF)
+set(HAVE_BROTLI OFF)
+if(CURL_BROTLI)
+  find_package(BROTLI QUIET)
+  if(BROTLI_FOUND)
+    set(HAVE_BROTLI ON)
+    list(APPEND CURL_LIBS ${BROTLI_LIBRARIES})
+    include_directories(${BROTLI_INCLUDE_DIRS})
+    list(APPEND CMAKE_REQUIRED_INCLUDES ${BROTLI_INCLUDE_DIRS})
+  endif()
+endif()
+
 #libSSH2
 option(CMAKE_USE_LIBSSH2 "Use libSSH2" ON)
 mark_as_advanced(CMAKE_USE_LIBSSH2)

lib/curl_config.h.cmake

@@ -398,6 +398,9 @@
 /* if zlib is available */
 #cmakedefine HAVE_LIBZ 1
 
+/* if brotli is available */
+#cmakedefine HAVE_BROTLI 1
+
 /* if your compiler supports LL */
 #cmakedefine HAVE_LL 1