Adjust how `slang` and `slangc` uses a `profile` to manage the stage of an entry-point (#4670)

* Fixes #4656

Changes:
1. Setting a profile via slangc no-longer sets an entry-point target-stage, this is to allow slangc to follow how the SLANG-API works (else `main` is assumed to be the default entry-point)
2. If the stage specified by a profile is not equal to the stage specified by a entry-point, we throw a capability error.
3. Resolving the stage of an entry point was changed to function (mostly) equally for when 0 entry-points are specified versus to when there are 1 or more.
4. changed capabilitySet Iterator so it is invalid if backing data is nullptr (although this should never happen, it would stop crashes in the worst case).

* remove the breaking change since it likely is going to be a lot more than just a simple change due to the implicit `main` and stage through `profile` code.

* print out profile name with errors

* use target's profile for printing

* change logic to print warning in a different method (account for more cases)

* set unknown stages

1 files changed, 16 insertions, 3 deletions

diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index 4670af9df..0f5a4b417 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -696,6 +696,7 @@ struct OptionsParser
 
     RawTarget* getCurrentTarget();
     void setProfileVersion(RawTarget* rawTarget, ProfileVersion profileVersion);
+    void setProfile(RawTarget* rawTarget, Profile profile);
     void addCapabilityAtom(RawTarget* rawTarget, CapabilityName atom);
     
     void setFloatingPointMode(RawTarget* rawTarget, FloatingPointMode mode);
@@ -1056,6 +1057,20 @@ void OptionsParser::setProfileVersion(RawTarget* rawTarget, ProfileVersion profi
     rawTarget->optionSet.setProfileVersion(profileVersion);
 }
 
+void OptionsParser::setProfile(RawTarget* rawTarget, Profile profile)
+{
+    if (rawTarget->optionSet.getProfile() != Profile::Unknown)
+    {
+        rawTarget->redundantProfileSet = true;
+
+        if (profile != rawTarget->optionSet.getProfile())
+        {
+            rawTarget->conflictingProfilesSet = true;
+        }
+    }
+    rawTarget->optionSet.setProfile(profile);
+}
+
 void OptionsParser::addCapabilityAtom(RawTarget* rawTarget, CapabilityName atom)
 {
     CapabilitySet capSet(atom);
@@ -1592,10 +1607,8 @@ SlangResult OptionsParser::_parseProfile(const CommandLineArg& arg)
     {
         auto profile = Profile(profileID);
 
-        setProfileVersion(getCurrentTarget(), profile.getVersion());
+        setProfile(this->getCurrentTarget(), profile);
 
-        // A `-profile` option that also specifies a stage (e.g., `-profile vs_5_0`)
-        // should be treated like a composite (e.g., `-profile sm_5_0 -stage vertex`)
         auto stage = profile.getStage();
         if (stage != Stage::Unknown)
         {