programmer: Add bitbanging programmer driver for Linux libgpiod

With this driver, any single board computer, old smartphone, etc. with
a few spare GPIOs can be used for flashrom.

Tested by reading of a 2048 kB flash chip on a Qualcomm MSM8916 SoC
@800 MHz, ran the following command:

time flashrom -p linux_gpiod:gpiochip=0,cs=18,sck=19,mosi=13,miso=56 -r test.bin

This command uses /dev/gpiochip0 with the specified GPIO numbers for the
SPI lines. All arguments are mandatory.

Output:
[...]
Found GigaDevice flash chip "GD25LQ16" (2048 kB, SPI) on linux_gpiod.
[...]
real    1m 33.96s

Change-Id: Icad3eb7764f28feaea51bda3a7893da724c86d06
Signed-off-by: Steve Markgraf <steve@steve-m.de>
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73290
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/util/manibuilder/Dockerfile.debian-debootstrap b/util/manibuilder/Dockerfile.debian-debootstrap
index e363fd2..3f5f0cb 100644
--- a/util/manibuilder/Dockerfile.debian-debootstrap
+++ b/util/manibuilder/Dockerfile.debian-debootstrap
@@ -6,7 +6,7 @@
 	apt-get -qq upgrade && \
 	apt-get -qqy install gcc make git doxygen ccache pkg-config \
 		libpci-dev libusb-dev libftdi-dev libusb-1.0-0-dev && \
-	{ apt-get -qqy install libjaylink-dev || true; } && \
+	{ apt-get -qqy install libjaylink-dev libgpiod-dev || true; } && \
 	apt-get clean
 
 ENV GIT_SSL_NO_VERIFY=1