Add --skip-soong-tests argument to soong_ui and use it in multiproduct_kati

There is no need for multiproduct_kati to run the tests for
every product, they don't vary by product config. --skip-soong-tests
can also be used for local development to run soong_build even if
the tests don't pass.

Bug: 156428456
Test: m --skip-soong-tests nothing
Change-Id: I9c00e3d1b6e51d17bb290339c3f124d4d1c9e69f
diff --git a/ui/build/config.go b/ui/build/config.go
index 82df8a0..e57c730 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -41,12 +41,13 @@
 	buildDateTime string
 
 	// From the arguments
-	parallel   int
-	keepGoing  int
-	verbose    bool
-	checkbuild bool
-	dist       bool
-	skipMake   bool
+	parallel       int
+	keepGoing      int
+	verbose        bool
+	checkbuild     bool
+	dist           bool
+	skipMake       bool
+	skipSoongTests bool
 
 	// From the product config
 	katiArgs        []string
@@ -526,6 +527,8 @@
 			c.verbose = true
 		} else if arg == "--skip-make" {
 			c.skipMake = true
+		} else if arg == "--skip-soong-tests" {
+			c.skipSoongTests = true
 		} else if len(arg) > 0 && arg[0] == '-' {
 			parseArgNum := func(def int) int {
 				if len(arg) > 2 {