Revert "tests: Allow specifying vboot source directory"

This reverts commit 7713a2f295d9ed9a7023a78e085ce190ee1203fe.

Reason for revert: breaks main branch

Change-Id: I2749bea9369c222e510b838e278c7797d5dce56e
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78852
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Patrick Georgi <patrick@coreboot.org>
diff --git a/tests/Makefile.common b/tests/Makefile.common
index 9cc79d7..e51d253 100644
--- a/tests/Makefile.common
+++ b/tests/Makefile.common
@@ -36,7 +36,7 @@
 
 TEST_INCLUDES += -I$(src) -I$(src)/include -I$(src)/commonlib/include \
 	-I$(src)/commonlib/bsd/include -I$(src)/arch/x86/include \
-	-I$(VBOOT_SOURCE)/firmware/include
+	-I$(top)/3rdparty/vboot/firmware/include
 
 # Path for Kconfig autoheader
 TEST_INCLUDES += -I$(dir $(TEST_KCONFIG_AUTOHEADER))