allow custom install/log/config path

[shrik3]

currently the paths to qkernel binary, log files and config files are hardcoded, among others:

pub const LOG_FILE_DEFAULT: &str = "/var/log/quark/quark.log";
pub const RAWLOG_FILE_DEFAULT: &str = "/var/log/quark/raw.log";
pub const LOG_FILE_FORMAT: &str = "/var/log/quark/{}.log";
pub const KERNEL_IMAGE: &'static str = "/usr/local/bin/qkernel_d.bin";
pub const KERNEL_IMAGE: &'static str = "/usr/local/bin/qkernel.bin";
pub const VDSO_PATH: &'static str = "/usr/local/bin/vdso.so";

to do this, we can pass install/log/config path as env variables and build the above path strings during compile time using rust's env! macro.

[shrik3]

The binary installation paths are fine, but the log path is tricky. The log path /var/log/quark/* is hardcoded everywhere, also in subprojects like qservice, qserverless ... etc.

This would be low priority then.

[shrik3]

This is necessary to build Quark packages for linux distributions, as they may not install binaries to the same path.