Fix compiling bas files relative to the CWD

Fix was pulled from QB64Official/qb64#17 by Cory Smith, I just added
tests around it.

Most (all?) compilers allow you to run the compiler from a separate
directory than the compiler itself is located in and compile source
files relative to that directory. QB64-PE however does not allow that,
for a variety of reasons it always search for the provided source file
relative to the location of the QB64-PE compiler rather than the CWD it
was run from. This is pretty unexpected behavior in a lot of cases, and
also doesn't give very helpful error messages either.

This change has us check if the source file exists at the given CWD
location, and if it does we will prepend the CWD to produce the correct
path to the file.

To test that this behavior works as expected I modified
`compile_test.sh` to compile from within the test directories using a
relative path directly to the test file, this fails with current QB64-PE
versions because it can't find the source file.

Additionally, I was unsure of whether this would impact the behavior of
`'$include`, so I added some tests around include that uses various
combinations of paths relative to QB64-PE and relative to the source
file being compiled, and they all find the files as expected so I think
it's fine.

source/qb64pe.bas

@@ -380,6 +380,9 @@ DIM SHARED compilelog$
 '$INCLUDE:'global\IDEsettings.bas'
 
 CMDLineFile = ParseCMDLineArgs$
+IF CMDLineFile <> "" AND _FILEEXISTS(_STARTDIR$ + "/" + CMDLineFile) THEN
+    CMDLineFile = _STARTDIR$ + "/" + CMDLineFile
+END IF
 
 IF ConsoleMode THEN
     _DEST _CONSOLE

tests/compile_tests.sh

@@ -56,9 +56,14 @@ do
         compilerFlags=$(cat "./tests/compile_tests/$category/$testName.flags")
     fi
 
+    pushd . >/dev/null
+    cd "./tests/compile_tests/$category"
+
     # -m and -q make sure that we get predictable results
-    "$QB64" $compilerFlags -m -q -x "./tests/compile_tests/$category/$testName.bas" -o "$EXE" 1>"$compileResultOutput"
+    "../../../$QB64" $compilerFlags -m -q -x "$testName.bas" -o "$EXE" 1>"../../../$compileResultOutput"
     ERR=$?
+
+    popd >/dev/null
     cp_if_exists ./internal/temp/compilelog.txt "$RESULTS_DIR/$category-$testName-compilelog.txt"
 
     if [ "$testType" == "success" ]; then

tests/compile_tests/extra/include_extra.bi

@@ -0,0 +1,2 @@
+
+PRINT "include_extra.bi was included!"

tests/compile_tests/extra/include_extra_include.bi

@@ -0,0 +1,12 @@
+
+' Include a file relative to the location of this file (which itself is included from elsewhere)
+
+' Both relative formats should work
+
+'$include:'./include_extra_target.bi'
+'$include:'include_extra_target.bi'
+
+' Absolute position relative to the compiler should work too
+
+'$include:'./tests/compile_tests/extra/include_extra_target.bi'
+'$include:'tests/compile_tests/extra/include_extra_target.bi'

tests/compile_tests/extra/include_extra_target.bi

@@ -0,0 +1,4 @@
+
+includeCount = includeCount + 1
+
+PRINT "include_extra_target.bi was included! Include count:"; includeCount

tests/compile_tests/include_paths/include_fixed_compile_location.bas

@@ -0,0 +1,10 @@
+$CONSOLE:ONLY
+
+' This include path is relative to the location of QB64-PE
+
+' Both relative path formats should work
+
+'$include:'./tests/compile_tests/extra/include_extra.bi'
+'$include:'tests/compile_tests/extra/include_extra.bi'
+
+SYSTEM

tests/compile_tests/include_paths/include_fixed_compile_location.output

@@ -0,0 +1,2 @@
+include_extra.bi was included!
+include_extra.bi was included!

tests/compile_tests/include_paths/include_multiple.bas

@@ -0,0 +1,12 @@
+$CONSOLE:ONLY
+
+' Include a file that itself includes another file. It does so in a relative
+' fashion
+
+Dim includeCount As Long
+
+'$include:'../extra/include_extra_include.bi'
+'$include:'./tests/compile_tests/extra/include_extra_include.bi'
+'$include:'tests/compile_tests/extra/include_extra_include.bi'
+
+SYSTEM

tests/compile_tests/include_paths/include_multiple.output

@@ -0,0 +1,12 @@
+include_extra_target.bi was included! Include count: 1 
+include_extra_target.bi was included! Include count: 2 
+include_extra_target.bi was included! Include count: 3 
+include_extra_target.bi was included! Include count: 4 
+include_extra_target.bi was included! Include count: 5 
+include_extra_target.bi was included! Include count: 6 
+include_extra_target.bi was included! Include count: 7 
+include_extra_target.bi was included! Include count: 8 
+include_extra_target.bi was included! Include count: 9 
+include_extra_target.bi was included! Include count: 10 
+include_extra_target.bi was included! Include count: 11 
+include_extra_target.bi was included! Include count: 12 

tests/compile_tests/include_paths/include_relative.bas

@@ -0,0 +1,7 @@
+$CONSOLE:ONLY
+
+' This include path is specified relative to the location of the current source file
+
+'$include:'../extra/include_extra.bi'
+
+SYSTEM

tests/compile_tests/include_paths/include_relative.output

@@ -0,0 +1 @@
+include_extra.bi was included!