fix(build): resolve BSD make compatibility issues

- Use absolute path ${.CURDIR}/test in main bmake.mk
- Replace automatic variable $< with explicit source filenames in test/bmake.mk
- Ensure proper directory navigation and source file compilation
- Fixes "undefined symbol: main" linker error on BSD systems

bmake.mk

@@ -50,4 +50,4 @@ clean:
 
 test: debug
 	@echo "=== Building and running stk tests ==="
-	cd test && ${MAKE} -f bmake.mk
+	cd ${.CURDIR}/test && ${MAKE} -f bmake.mk

test/bmake.mk

@@ -17,10 +17,10 @@ MODULE_EXT = .so
 all: test
 
 test_program: test.c
-	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+	$(CC) $(CFLAGS) -o $@ test.c $(LDFLAGS)
 
 test_mod$(MODULE_EXT): test_mod.c
-	$(CC) $(CFLAGS) -fPIC -shared -o $@ $<
+	$(CC) $(CFLAGS) -fPIC -shared -o $@ test_mod.c
 
 setup:
 	@mkdir -p mods