A team member found the problem. Here is the description:
The error was the incorrect inclusion of INITRAMFS. INITRAMFS is a kernel option that is controlled by buildroot. A simple intro to INITRAMFS is described below:
│ CONFIG_BLK_DEV_INITRD:
│
│ The initial RAM filesystem is a ramfs which is loaded by the
│ boot loader (loadlin or lilo) and that is mounted as root
│ before the normal boot procedure. It is typically used to
│ load modules needed to mount the "real" root file system,
│ etc. See <file:Documentation/initrd.txt> for details.
│
│ If RAM disk support (BLK_DEV_RAM) is also included, this
│ also enables initial RAM disk (initrd) support and adds
│ 15 Kbytes (more on some other architectures) to the kernel size.
│
│ If unsure say Y.
│
This is also the source of the …/outoutp/images/rootfs.cpio file (which is no longer necessary).
The buildroot .config files were the same between /Testsuite and /Developer, but the /linux/linux-kernel files/.config files were different. /Testsuite changed the INITRAMFS setting on the kernel configuration itself, bypassing buildroot.
This also explains the double compilation issue (not tested). /testsuite sets up both Buildroot .config and the kernel .config. During make of Buildroot, the Buildroot .config changes the kernel .config variable INITRAMFS to Y then compiles the kernel. The compiled kernel will not load the jffs2 partition. The second time /testsuite is run, buildroot .config and the kernel .config are loaded again. Buildroot .config has not changed so it is skipped by make, so buildroot does not change the kernel INITRAMFS
