Add a flag to build for all supported platforms

main.go

@@ -35,6 +35,7 @@ func realMain() int {
 	flags.Var(platformFlag.ArchFlagValue(), "arch", "arch to build for or skip")
 	flags.Var(platformFlag.OSArchFlagValue(), "osarch", "os/arch pairs to build for or skip")
 	flags.Var(platformFlag.OSFlagValue(), "os", "os to build for or skip")
+	flags.BoolVar(&platformFlag.All, "all", false, "build for all known os/arch combinations")
 	flags.StringVar(&ldflags, "ldflags", "", "linker flags")
 	flags.StringVar(&tags, "tags", "", "go build tags")
 	flags.StringVar(&outputTpl, "output", "{{.Dir}}_{{.OS}}_{{.Arch}}", "output path")
@@ -217,6 +218,7 @@ Options:
   -os=""              Space-separated list of operating systems to build for
   -osarch=""          Space-separated list of os/arch pairs to build for
   -osarch-list        List supported os/arch pairs for your Go version
+  -all                Build for all know os/arch combinations
   -output="foo"       Output path template. See below for more info
   -parallel=-1        Amount of parallelism, defaults to number of CPUs
   -gocmd="go"         Build command, defaults to Go

platform_flag.go

@@ -12,6 +12,7 @@ type PlatformFlag struct {
 	OS     []string
 	Arch   []string
 	OSArch []Platform
+	All    bool
 }
 
 // Platforms returns the list of platforms that were set by this flag.
@@ -127,7 +128,7 @@ func (p *PlatformFlag) Platforms(supported []Platform) []Platform {
 	if prefilter == nil {
 		prefilter = make([]Platform, 0, len(supported))
 		for _, v := range supported {
-			if v.Default {
+			if v.Default || p.All {
 				add := v
 				add.Default = false
 				prefilter = append(prefilter, add)