expr_parser: support ':' operator

Similar to '==' but compiles the RHS into a regular expression
and attempts to match whatever is in the environment against it.

Change-Id: I7a03452ef88d067b62661d14dc6f42273de436fa
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/scripts/sanitycheck b/scripts/sanitycheck
index 1d849be..3b80d0c 100755
--- a/scripts/sanitycheck
+++ b/scripts/sanitycheck
@@ -80,6 +80,7 @@
                  | symbol ">=" number
                  | symbol "<=" number
                  | symbol "in" list
+                 | symbol ":" string
                  | symbol
 
     list ::= "[" list_contents "]"
@@ -110,6 +111,14 @@
 
         filter = not ARCH in ["x86", "arc"]
 
+    The ':' operator compiles the string argument as a regular expression,
+    and then returns a true value only if the symbol's value in the environment
+    matches. For example, if CONFIG_SOC="quark_se" then
+
+        filter = CONFIG_SOC : "quark.*"
+
+    Would match it.
+
 Architectures and platforms are defined in an archtecture configuration
 file which are stored by default in scripts/sanity_chk/arches/. These
 each define an [arch] block with the following key/value pairs: