This means that all modules and applications by default add -rpath flag
to linker calls for executables but not for shared libraries. So all
executables will have RUNPATH set as before (unless LINK_USE_RPATH is
explicitly set to NO) but shared libraries won't, which is exactly the
behavior we want so that for our soft IOCs we can set the RUNPATH to "."
and have self-contained installations with no hard-coded paths that only
exist on the build host but not on the target host.

This is stupid and causes lots of unnecessary incompatibilities.

This makes it possible to specify a location different from "/usr" for the
RTEMS cross tools. The file RTEMS_TOOLS is created in RTEMS-BUILD-TOOL and
contains the definition of the environment variable RTEMS_TOOLS.

It turned out that MSI_3_15 has several bugs that makes it much too
difficult to port applications.

The build rules for these dependency files are crap and removing the targets
from DBDDEPENDS_FILES is the simplest way to disable them. They call msi
with the -D option which generates incomplete dependencies and fails with
ugly error messages for generated template files. A better way to generate
dependencies for db and template files is contained in the RULES_DB
installed by the BESSYRULES module.

This rule caused (non-fatal but ugly) failures when a Makefiles specifies a
non-empty DBD, but no xxx_DBD.

These collide with our existing build rules.

Otherwise, when IOCs are CA clients, they will use the IP address as the
host name, which doesn't work with our security.acf files.

* use TFTP for st.cmd, but only prepend /TFTP/BOOTP_HOST to the path
  we get from rtems_bsdnet_bootp_cmdline
* also initialize NFS but don't mount anything yet

In particular, this increases CONFIGURE_EXECUTIVE_RAM_SIZE from 2 to 5 MB,
solving resource problems (too many semaphores, threads) on some IOCs.