ffmpeg: Add support for pic compilation (#1211)

* ffmpeg: Add support for pic compilation

* Update xmake.lua

Co-authored-by: ruki <waruqi@gmail.com>

packages/f/ffmpeg/xmake.lua

@@ -56,6 +56,11 @@ package("ffmpeg")
                 package:add("deps", dep)
             end
         end
+        -- https://www.ffmpeg.org/platform.html#toc-Advanced-linking-configuration
+        if package:config("pic") ~= false then
+            package:add("shflags", "-Wl,-Bsymbolic")
+            package:add("ldflags", "-Wl,-Bsymbolic")
+        end
     end)
 
     on_install("windows|x64", "mingw|x86_64", function (package)
@@ -86,6 +91,9 @@ package("ffmpeg")
         else
             table.insert(configs, "--disable-debug")
         end
+        if package:config("pic") ~= false then
+            table.insert(configs, "--enable-pic")
+        end
         if package:is_plat("android") then
             import("core.base.option")
             import("core.tool.toolchain")

packages/x/x264/xmake.lua

@@ -8,12 +8,13 @@ package("x264")
     add_versions("v2018.09.25", "545de2ffec6ae9a80738de1b2c8cf820249a2530")
 
     add_deps("nasm")
+    add_configs("toolchains", {readonly = true, description = "Set package toolchains only for cross-compilation."})
 
     add_syslinks("pthread", "dl")
     on_install("linux", "macosx", function (package)
         local configs = {"--disable-avs", "--disable-lsmash", "--disable-lavf", "--disable-bashcompletion"}
         table.insert(configs, "--enable-" .. (package:configs("shared") and "shared" or "static"))
-        if package:config("pic") then
+        if package:config("pic") ~= false then
             table.insert(configs, "--enable-pic")
         end
         import("package.tools.autoconf").install(package, configs)