ProjectExplorer: Add support for new RISC-V architecture

This commit adds new ProjectExplorer::Abi::RiscVArchitecture
entry for the RISC-V architecture:

 * https://riscv.org/

Change-Id: I0cd73cca22a2852203372efbccc51d74581d8f50
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/abi.cpp

@@ -749,6 +749,8 @@ QString Abi::toString(const Architecture &a)
         return QLatin1String("rx");
     case K78Architecture:
         return QLatin1String("78k");
+    case RiscVArchitecture:
+        return QLatin1String("riscv");
     case UnknownArchitecture:
         Q_FALLTHROUGH();
     default:
@@ -905,6 +907,8 @@ Abi::Architecture Abi::architectureFromString(const QStringRef &a)
         return RxArchitecture;
     if (a == "78k")
         return K78Architecture;
+    if (a == "riscv")
+        return RiscVArchitecture;
     else if (a == "xtensa")
         return XtensaArchitecture;
     if (a == "asmjs")

src/plugins/projectexplorer/abi.h

@@ -69,6 +69,7 @@ public:
         Rh850Architecture,
         RxArchitecture,
         K78Architecture,
+        RiscVArchitecture,
         UnknownArchitecture
     };