CppEditor: Allow filtering of unsupported -mcpu flags

Also hardcode one that we use with Boot2Qt.

Fixes: QTCREATORBUG-29304
Change-Id: I3dd425cae5eb87ad5e14a607431d9f7225efc566
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/cppeditor/compileroptionsbuilder.cpp

@@ -64,6 +64,13 @@ static QString defineDirectiveToDefineOption(const Macro &macro)
     return QString::fromUtf8(option);
 }
 
+static QStringList cpuBlacklist()
+{
+    QStringList blacklist = qtcEnvironmentVariable("QTC_CLANGD_CPU_BLACKLIST")
+                                .split(':', Qt::SkipEmptyParts);
+    return blacklist << "cortex-a72.cortex-a53"; // See QTCREATORBUG-29304
+}
+
 QStringList XclangArgs(const QStringList &args)
 {
     QStringList options;
@@ -270,6 +277,7 @@ void CompilerOptionsBuilder::addPicIfCompilerFlagsContainsIt()
 void CompilerOptionsBuilder::addCompilerFlags()
 {
     add(m_compilerFlags.flags);
+    removeUnsupportedCpuFlags();
 }
 
 void CompilerOptionsBuilder::addMsvcExceptions()
@@ -375,6 +383,17 @@ void CompilerOptionsBuilder::addIncludeFile(const QString &file)
     }
 }
 
+void CompilerOptionsBuilder::removeUnsupportedCpuFlags()
+{
+    const QStringList blacklist = cpuBlacklist();
+    for (auto it = m_options.begin(); it != m_options.end();) {
+        if (it->startsWith("-mcpu=") && blacklist.contains(it->mid(6)))
+            it = m_options.erase(it);
+        else
+            ++it;
+    }
+}
+
 void CompilerOptionsBuilder::addIncludedFiles(const QStringList &files)
 {
     for (const QString &file : files) {

src/plugins/cppeditor/compileroptionsbuilder.h

@@ -87,6 +87,7 @@ private:
     QStringList wrappedMingwHeadersIncludePath() const;
     QByteArray msvcVersion() const;
     void addIncludeFile(const QString &file);
+    void removeUnsupportedCpuFlags();
 
 private:
     const ProjectPart &m_projectPart;