symbol files: introduce more switches for debugging

compiler/options.nim

@@ -48,7 +48,6 @@ type                          # please make sure we have under 32 options
     optGenScript,             # generate a script file to compile the *.c files
     optGenMapping,            # generate a mapping file
     optRun,                   # run the compiled project
-    optSymbolFiles,           # use symbol files for speeding up compilation
     optCaasEnabled            # compiler-as-a-service is running
     optSkipConfigFile,        # skip the general config file
     optSkipProjConfigFile,    # skip the project's config file
@@ -147,12 +146,19 @@ var
   newDestructors*: bool
   gDynlibOverrideAll*: bool
 
+type
+  SymbolFilesOption* = enum
+    disabledSf, enabledSf, writeOnlySf, readOnlySf
+
+var gSymbolFiles*: SymbolFilesOption
+
 proc importantComments*(): bool {.inline.} = gCmd in {cmdDoc, cmdIdeTools}
 proc usesNativeGC*(): bool {.inline.} = gSelectedGC >= gcRefc
 template preciseStack*(): bool = gPreciseStack
 
 template compilationCachePresent*: untyped =
-  {optCaasEnabled, optSymbolFiles} * gGlobalOptions != {}
+  gSymbolFiles in {enabledSf, writeOnlySf}
+#  {optCaasEnabled, optSymbolFiles} * gGlobalOptions != {}
 
 template optPreserveOrigSource*: untyped =
   optEmbedOrigSrc in gGlobalOptions