ProjectExplorer: Remove QTC_CPU override

QTC_CPU was broken in qmake and never worked there. Qbs never implemented
the override properly, so neither did it work there.

Use QSysInfo to retrieve information on CPU that Qt was built for and use
that in the hostAbi.

Change-Id: I298c15b2263c9eaf343a93037229de64e90c36ef
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Jake Petroules <jake.petroules@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/projectexplorer/abi.cpp

@@ -50,6 +50,27 @@ namespace ProjectExplorer {
 // Helpers
 // --------------------------------------------------------------------------
 
+static Abi::Architecture architectureFromQt()
+{
+    const QString arch = QSysInfo::buildCpuArchitecture();
+    if (arch.startsWith("arm"))
+        return Abi::ArmArchitecture;
+    if (arch.startsWith("x86") || arch == "i386")
+        return Abi::X86Architecture;
+    if (arch == "ia64")
+        return Abi::ItaniumArchitecture;
+    if (arch.startsWith("mips"))
+        return Abi::MipsArchitecture;
+    if (arch.startsWith("power"))
+        return Abi::PowerPCArchitecture;
+    if (arch.startsWith("sh")) // Not in Qt documentation!
+        return Abi::ShArchitecture;
+    if (arch.startsWith("avr")) // Not in Qt documentation!
+        return Abi::AvrArchitecture;
+
+    return Abi::UnknownArchitecture;
+}
+
 static quint8 getUint8(const QByteArray &data, int pos)
 {
     return static_cast<quint8>(data.at(pos));
@@ -838,7 +859,7 @@ Abi::OSFlavor Abi::flavorForMsvcVersion(int version)
 
 Abi Abi::hostAbi()
 {
-    Architecture arch = QTC_CPU; // define set by qmake
+    Architecture arch = architectureFromQt();
     OS os = UnknownOS;
     OSFlavor subos = UnknownFlavor;
     BinaryFormat format = UnknownFormat;

src/plugins/projectexplorer/projectexplorer.pro

@@ -332,11 +332,4 @@ journald {
 
 RESOURCES += projectexplorer.qrc
 
-# Some way to override the architecture used in Abi:
-!isEmpty($$(QTC_CPU)) {
-    DEFINES += QTC_CPU=$$(QTC_CPU)
-} else {
-    DEFINES += QTC_CPU=X86Architecture
-}
-
 DEFINES += PROJECTEXPLORER_LIBRARY

src/plugins/projectexplorer/projectexplorer.qbs

@@ -15,8 +15,6 @@ Project {
         Depends { name: "TextEditor" }
         Depends { name: "app_version_header" }
 
-        cpp.defines: base.concat("QTC_CPU=X86Architecture")
-
         Group {
             name: "General"
             files: [