Fix -o to be relative to _STARTDIR$ when source file is

In 094a8c82 we added the ability to compile a source file relative to
_STARTDIR$ instead of the location of the qb64pe executable. This change
fixes `-o` so that it is also treated as relative to _STARTDIR$ when the
provided source file is.

Note that this is not a real behavior change because if the provided
source file is relative to the qb64pe executable then `-o` will be as
well, which matches the previous behavior. The cases where it is made
relative to _STARTDIR$ all produced errors until 094a8c82 was done, so
there was no previous defined behavior.

source/qb64pe.bas

@@ -379,9 +379,12 @@ DIM SHARED compilelog$
 
 '$INCLUDE:'global\IDEsettings.bas'
 
+DIM OutputIsRelativeToStartDir AS LONG
+
 CMDLineFile = ParseCMDLineArgs$
 IF CMDLineFile <> "" AND _FILEEXISTS(_STARTDIR$ + "/" + CMDLineFile) THEN
     CMDLineFile = _STARTDIR$ + "/" + CMDLineFile
+    OutputIsRelativeToStartDir = -1
 END IF
 
 IF ConsoleMode THEN
@@ -12319,19 +12322,38 @@ IF idemode = 0 AND No_C_Compile_Mode = 0 THEN
         path.out$ = getfilepath$(outputfile_cmd$)
         f$ = MID$(outputfile_cmd$, LEN(path.out$) + 1)
         file$ = RemoveFileExtension$(f$)
-        IF LEN(path.out$) THEN
+
+        IF LEN(path.out$) OR OutputIsRelativeToStartDir THEN
+            currentdir$ = _CWD$
+
+            IF OutputIsRelativeToStartDir THEN
+                ' This CHDIR makes the next CHDIR relative to _STARTDIR$
+                ' We do this if the provided source file was also relative to _STARTDIR$
+                CHDIR _STARTDIR$
+
+                ' If there was no provided path then that is the same as the
+                ' output file being directly in _STARTDIR$. Assigning it here
+                ' is perfectly fine and avoids failing the error check below
+                ' with a blank string.
+                IF LEN(path.out$) = 0 THEN
+                    path.out$ = _STARTDIR$
+                END IF
+            END IF
+
             IF _DIREXISTS(path.out$) = 0 THEN
                 PRINT
                 PRINT "Can't create output executable - path not found: " + path.out$
                 IF ConsoleMode THEN SYSTEM 1
                 END 1
             END IF
-            currentdir$ = _CWD$
+
             CHDIR path.out$
             path.out$ = _CWD$
             CHDIR currentdir$
+
             IF RIGHT$(path.out$, 1) <> pathsep$ THEN path.out$ = path.out$ + pathsep$
             path.exe$ = path.out$
+
             SaveExeWithSource = -1 'Override the global setting if an output file was specified
         END IF
     END IF

tests/compile_tests.sh

@@ -60,7 +60,7 @@ do
     cd "./tests/compile_tests/$category"
 
     # -m and -q make sure that we get predictable results
-    "../../../$QB64" $compilerFlags -m -q -x "$testName.bas" -o "$EXE" 1>"../../../$compileResultOutput"
+    "../../../$QB64" $compilerFlags -q -m -x "$testName.bas" -o "../../../$EXE" 1>"../../../$compileResultOutput"
     ERR=$?
 
     popd >/dev/null