Check for all missing tools at once

Instead of terminating tool/tool_chain when finding the first
missing tool, this patch runs all checks to completion before
bailing out. This eases finding missing programs, because the
user has to run the script only once to get a list of all missing
software.

Fixes #1046
Fixes #1047
base: extend thread test for stack alignment
os: handle ipc error in server framework

When using the server framework, it might happen that the main thread
tries to forward a signal to the entrypoint, while the context of that
signal is already destroyed. In that case the main thread will get an
ipc error exception as result.

Related to #113
block: cache between one client and one device

This block cache component acts as a block device for a single client.
It uses fixed 4K blocks as caching granularity, thereby implicitly reads
ahead whenever a client requests lesser amount of blocks. Currently,
it only supports a least-recently-used replacement policy.

Fixes #113