feat: add cross-compilation support with --target flag

- Updated build and run commands to accept a --target option for specifying target platforms.
- Enhanced documentation to include cross-compilation usage and supported targets.
- Modified configuration to allow target-specific settings and toolchains.
- Introduced a new test command to run project tests with specified profiles and targets.
- Improved handling of target directories and output structure for different platforms.
- Added support for multiple targets in the configuration file.
- Implemented inheritance for workspace and dependencies based on target and profile.

src/core/builder/unix_cc.rs

@@ -155,8 +155,10 @@ fn build_objects(
             if !ctx.standard.is_empty() && ctx.language.to_lowercase() != "asm" {
                 cmd.arg(format!("-std={}", ctx.standard));
             }
-            for flag in default_flags(ctx.profile) {
-                cmd.arg(flag);
+            if ctx.cflags.is_empty() {
+                for flag in default_flags(ctx.profile) {
+                    cmd.arg(flag);
+                }
             }
             for flag in ctx.cflags {
                 cmd.arg(flag);