ProjectExplorer: Introduce new STM8 architecture

This architecture is useful in programming of a bare-metal
devices, based on 8-bit microcontrollers from STMicroelectronics:

* https://en.wikipedia.org/wiki/STM8

Change-Id: Ie5d28a29aaa36e65a29bb96f988e6ee4327e1e9e
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/abi.cpp

@@ -691,6 +691,8 @@ QString Abi::toString(const Architecture &a)
         return QLatin1String("sh");
     case AsmJsArchitecture:
         return QLatin1String("asmjs");
+    case Stm8Architecture:
+        return QLatin1String("stm8");
     case UnknownArchitecture:
         Q_FALLTHROUGH();
     default:
@@ -827,6 +829,8 @@ Abi::Architecture Abi::architectureFromString(const QStringRef &a)
         return ItaniumArchitecture;
     if (a == "sh")
         return ShArchitecture;
+    if (a == "stm8")
+        return Stm8Architecture;
     else if (a == "xtensa")
         return XtensaArchitecture;
     if (a == "asmjs")

src/plugins/projectexplorer/abi.h

@@ -59,6 +59,7 @@ public:
         XtensaArchitecture,
         Mcs51Architecture,
         AsmJsArchitecture,
+        Stm8Architecture,
         UnknownArchitecture
     };