add package libbacktrace (#639)

* add package libbacktrace

* use autoconf instead of make

* add on_test for libbacktrace

* shared, static, pic

packages/l/libbacktrace/xmake.lua

@@ -0,0 +1,23 @@
+package("libbacktrace")
+
+    set_homepage("https://github.com/ianlancetaylor/libbacktrace")
+    set_description("A C library that may be linked into a C/C++ program to produce symbolic backtraces")
+
+    add_urls("https://github.com/ianlancetaylor/libbacktrace.git")
+    add_versions("v1.0", "d0f5e95a87a4d3e0a1ed6c069b5dae7cbab3ed2a")
+
+    on_install("linux", "macosx", function (package)
+        local configs = {}
+        local cxflags = {}
+        table.insert(configs, "--enable-shared=" .. (package:config("shared") and "yes" or "no"))
+        table.insert(configs, "--enable-static=" .. (package:config("shared") and "no" or "yes"))
+        if package:config("pic") ~= false then
+            table.insert(cxflags, "-fPIC")
+        end
+        import("package.tools.autoconf").install(package, configs, {cxflags = cxflags})
+    end)
+
+    on_test(function (package)
+        assert(package:has_cfuncs("backtrace_create_state", {includes = "backtrace.h"}))
+        assert(package:has_cfuncs("backtrace_full", {includes = "backtrace.h"}))
+    end)