fix(libvpx): fix some errors

packages/l/libvpx/utils.lua

@@ -41,7 +41,7 @@ function get_target(package)
     local arch = package:targetarch()
     if arch:startswith("arm64") then
         arch = "arm64"
-    elseif arch == "armeabi-v7a" then
+    elseif arch == "armeabi-v7a" or arch == "arm" then
         arch = "armv7"
     elseif arch == "x64" then
         arch = "x86_64"
@@ -63,7 +63,7 @@ function get_target(package)
     end
 
     local cc = path.basename(compiler.compcmd("foo.c")):split(" ", {plain = true})[1]:lower()
-    if cc == "clang" or cc == "emcc" then
+    if cc == "clang" or cc == "emcc" or cc:endswith("-gcc") then
         cc = "gcc"
     elseif cc == "cl" then
         cc = "vs"
@@ -72,12 +72,12 @@ function get_target(package)
     local matched_plats
     matched_plats = _filter(platforms, function (p) return p[1] == arch end)
     local tmp = _filter(matched_plats, function (p) return p[2] == os end)
-    matched_plats = #tmp == 0 and _filter(matched_plats, function (p) return p[2]:startswith(plat) end) or tmp
+    matched_plats = #tmp == 0 and _filter(matched_plats, function (p) return p[2] and  p[2]:startswith(os) end) or tmp
     tmp = nil
     if #matched_plats == 0 then
-        cprint("${yellow}warning: ${clear}no matching platform for " .. os .. "-" .. arch .. " " .. cc .. ", use " .. default_plat)
+        cprint("${yellow}warning: ${clear}no matching platform for ${blue}" .. os .. " " .. arch .. " " .. cc .. "${clear}, use " .. default_plat)
     end
-    local result = _join(_find(platforms, function(p) return p[3] == cc end) or _find(platforms, function(p) return p[3]:startswith(cc) end) or platforms[1], "-")
+    local result = _join(_find(platforms, function(p) return p[3] == cc end) or _find(platforms, function(p) return p[3] and p[3]:startswith(cc) end) or matched_plats[1], "-")
     cprint("${green}info: ${clear}use target platform ${blue}" .. result .. "${clear}")
     return result
 end