ci: install target libc headers for Debian cross builds

The Debian cross jobs install packages with --no-install-recommends.
The cross compiler packages only recommend the target libc development
headers, so the jobs can reach the compile step without basic headers
such as sys/file.h, sys/socket.h, and bits/wordsize.h.

Install libc6-dev for the target architecture explicitly. This provides
the normal system headers needed by the cross compiler and keeps the CI
setup independent of package recommendations.

Signed-off-by: Bjorn Andersson <bjorn.andersson@oss.qualcomm.com>

ci/debian.cross-compile.sh

@@ -19,6 +19,7 @@ dpkg --add-architecture $ARCH
 apt update
 
 apt install -y --no-install-recommends \
+	libc6-dev:${ARCH} \
 	libftdi1-dev:${ARCH} \
 	libudev-dev:${ARCH} \
 	libyaml-dev:${ARCH} \