fix:[CI-14845]: support for build args which has comma seperated values

cmd/drone-docker/custom_string_slice.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"strings"
+)
+
+// CustomStringSliceFlag is like a regular StringSlice flag but with
+// semicolon as a delimiter
+type CustomStringSliceFlag struct {
+	Value []string
+}
+
+func (f *CustomStringSliceFlag) GetValue() []string {
+	if f.Value == nil {
+		return make([]string, 0)
+	}
+	return f.Value
+}
+
+func (f *CustomStringSliceFlag) String() string {
+	if f.Value == nil {
+		return ""
+	}
+	return strings.Join(f.Value, ";")
+}
+
+func (f *CustomStringSliceFlag) Set(v string) error {
+	for _, s := range strings.Split(v, ";") {
+		s = strings.TrimSpace(s)
+		f.Value = append(f.Value, s)
+	}
+	return nil
+}