bash: fix static build

When building bash statically, configure does not initialize the
SHOBJ_STATUS variable. The SHOBJ_STATUS make variable in
examples/loadables/Makefile.in must resolve to either 'supported' or
'unsupported'. Otherwise, the install-$(SHOBJ_STATUS) target does not
exist.

This leads to the following build failure:

make[2]: Entering directory '.../output/build/bash-4.4/examples/loadables'
make[2]: *** No rule to make target 'install-', needed by 'install'.  Stop.
make[2]: Leaving directory '.../output/build/bash-4.4/examples/loadables'
Makefile:793: recipe for target 'install' failed

with the following defconfig:

BR2_arm=y
BR2_STATIC_LIBS=y
BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
BR2_PACKAGE_BASH=y

Note that this doesn't terminate the build so it's not detected as an
error by the autobuilders.

Set SHOBJ_STATUS in the configure environment as a workaround.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>