ProjectExplorer: Add support for new M68K architecture

This commit adds new ProjectExplorer::Abi::M68KArchitecture
entry for the M68K (aka new NXP ColdFire) architecture:

 * https://wiki.osdev.org/M68k_Overview
 * https://www.nxp.com/products/product-information/ip-block-licensing/coldfire-32-bit-processors:COLDFIRE-32-BIT-PROCESSORS

Change-Id: I84a70b2d127f207bdff5cd085890def1fe28b17d
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/abi.cpp

@@ -755,6 +755,8 @@ QString Abi::toString(const Architecture &a)
         return QLatin1String("rx");
     case K78Architecture:
         return QLatin1String("78k");
+    case M68KArchitecture:
+        return QLatin1String("m68k");
     case RiscVArchitecture:
         return QLatin1String("riscv");
     case UnknownArchitecture:
@@ -913,6 +915,8 @@ Abi::Architecture Abi::architectureFromString(const QStringRef &a)
         return RxArchitecture;
     if (a == "78k")
         return K78Architecture;
+    if (a == "m68k")
+        return M68KArchitecture;
     if (a == "riscv")
         return RiscVArchitecture;
     else if (a == "xtensa")