Add docs for common issues

[tonistiigi]

For example:

• Build triggers when installing packages Alpine: some dev packages raise triggers that fail #36
• /lib/ld-musl-aarch64.so.1: No such file or directory Cross-compile fails in Alpine #34
• Error that shows up when the user forgets to install libc/libgcc for the target architecture.

[Entropy512]

As far as documentation, I ran into a similar issue to #34 - cyclonedds' official recommendation is to build cyclonedds for the host, then to build for a cross target, which will find the host idlc binary

This double-build scenario works on a non-native target, but the double-build process interferes with itself on a non-native target (although I did not try building a redundant/vestigial idlc for the target, as cyclonedds installs different cmake configurations depending on whether idlc was built or not...)

protobuf is similar - it requires a double-build in cross compile environments. It turns out that since idlc/protoc/etc aren't hugely CPU-consuming, it winds up much easier to do
QEMU_LD_PREFIX=/$(xx-info) make

for a single build for the target arch

[tonistiigi]

@Entropy512 If the software you are building is common enough to be useful for others, then feel free to post the details here(or under discussions). Either the Dockerfiles you have built or Dockerfiles you have tried but don't know how to get working.