abuild: Fix board variant handling

Problem:
Me: $ util/abuild/abuild -t asus/p2b -b p2b-ls
abuild: No such target: asus/p2b, variant: p2b-ls

Cause: We identify boards and variants using path names in tree, so
I type in the test command above. abuild identifies all board variants
the Kconfig way, in all caps and all underscores.

Result: Expectation gap and abuild can't find anything where we expect
it to. All variants with a hyphen in their names are affected.

Fix: Add a substitution to replace hyphens with underscores.

Test: I get my abuild with the command above, even a variant-specific
test config works.

Change-Id: I10d5b471dac41c50a85c4a309ec561b02687bb9a
Signed-off-by: Keith Hui <buurin@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41918
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

util/abuild/abuild

@@ -181,7 +181,7 @@ function normalize_target
 	local targets
 	local VARIANT_UC
 
-	VARIANT_UC=$(echo "${variant}" | tr '[:lower:]' '[:upper:]')
+	VARIANT_UC=$(echo "${variant}" | tr '[:lower:]' '[:upper:]' | tr '-' '_')
 
 	targets=$(get_mainboards "$1")
 	if [ -n "$targets" ]; then