Fix whitespace in soong_config_set calls

In make, soong_config_set uses an $(eval) to set it's value, expanding
the value of the soong config variable _before_ evaluating the value.
Because of this, make will strip trailing whitespace like it does on
regular assignments.

Make rbcrun match this behavior.

Test: ./out/rbcrun ./build/make/tests/run.rbc
Change-Id: I907e85cdf50f6fac54331c0d1044f0d53bec22ed

core/product_config.rbc

@@ -394,6 +394,10 @@ def _soong_config_namespace(g, nsname):
 def _soong_config_set(g, nsname, var, value):
     """Assigns the value to the variable in the namespace."""
     _soong_config_namespace(g, nsname)
+    if type(value) == "string":
+        # Trim right spaces, because in make the variable is set in an $(eval),
+        # which will ignore trailing spaces.
+        value = value.rstrip(" ")
     g[_soong_config_namespaces_key][nsname][var]=value
 
 def _soong_config_append(g, nsname, var, value):

tests/product.rbc

@@ -54,6 +54,7 @@ def init(g, handle):
   rblf.soong_config_append(g, "NS1", "v2", "def")
   rblf.soong_config_set(g, "NS2", "v3", "abc")
   rblf.soong_config_set(g, "NS2", "v3", "xyz")
+  rblf.soong_config_set(g, "NS2", "v4", "xyz   ")
 
   rblf.mkdist_for_goals(g, "goal", "dir1/file1:out1 dir1/file2:out2")
   rblf.mkdist_for_goals(g, "goal", "dir2/file2:")

tests/run.rbc

@@ -144,7 +144,8 @@ assert_eq(
             "v2": "def"
         },
         "NS2": {
-            "v3": "xyz"
+            "v3": "xyz",
+            "v4": "xyz"
         }
     },
     {k:v for k, v in sorted(ns.items()) }