util/kconfig: Add pre-built parser

It avoids the dependency on bison/flex, minimally speeds up the build
and also works around weird race conditions in some versions of bison
that need more investigation.

The issue this avoids manifests as a build error when creating
parser.tab.c:

    input in flex scanner failed
    make: *** [util/kconfig/Makefile.inc:66: build/util/kconfig/parser.tab.c] Error 2

Since the error happens within bison the alternative would be to make
bison part of our crossgcc environment to ensure that no broken OS
build is used.

BUG=b:197515860
TEST=things build with bison not installed

Change-Id: Ib35dfb7beafc0a09dc333e962b1e3f33df46a854
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57409
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/Kconfig

@@ -112,7 +112,7 @@ config FMD_GENPARSER
 	  Otherwise, say N to use the provided pregenerated scanner/parser.
 
 config UTIL_GENPARSER
-	bool "Generate SCONFIG & BINCFG parser using flex and bison"
+	bool "Generate parsers for bincfg, sconfig and kconfig locally"
 	default n
 	help
 	  Enable this option if you are working on the sconfig device tree