[libcalamares] Improve process logging

- Don't insert a space before the output of a process
 - To do this, suppress space and quoting on the output, and to do
   that move the labeling-output for warnings and errors into
   the constructor (so that an idiomatic .nospace() does the right thing).

src/libcalamares/utils/CalamaresUtilsSystem.cpp

@@ -174,7 +174,7 @@ System::runCommand(
 
     if ( !process.waitForFinished( timeoutSec ? ( timeoutSec * 1000 ) : -1 ) )
     {
-        cWarning() << "Timed out. Output so far:\n" <<
+        cWarning().noquote().nospace() << "Timed out. Output so far:\n" <<
             process.readAllStandardOutput();
         return -4;
     }
@@ -183,7 +183,7 @@ System::runCommand(
 
     if ( process.exitStatus() == QProcess::CrashExit )
     {
-        cWarning() << "Process crashed. Output so far:\n" << output;
+        cWarning().noquote().nospace() << "Process crashed. Output so far:\n" << output;
         return -1;
     }
 
@@ -192,7 +192,7 @@ System::runCommand(
     if ( ( r != 0 ) || Calamares::Settings::instance()->debugMode() )
     {
         cDebug() << "Target cmd:" << args;
-        cDebug().noquote() << "Target output:\n" << output;
+        cDebug().noquote().nospace() << "Target output:\n" << output;
     }
     return ProcessResult(r, output);
 }

src/libcalamares/utils/Logger.h

@@ -56,6 +56,10 @@ namespace Logger
     public:
         CDebug( unsigned int debugLevel = LOGDEBUG ) : CLog( debugLevel )
         {
+            if ( debugLevel <= LOGERROR )
+                *this << "ERROR:";
+            else if ( debugLevel <= LOGWARNING )
+                *this << "WARNING:";
         }
         virtual ~CDebug();
     };
@@ -173,7 +177,7 @@ namespace Logger
 }
 
 #define cDebug Logger::CDebug
-#define cWarning() Logger::CDebug(Logger::LOGWARNING) << "WARNING:"
-#define cError() Logger::CDebug(Logger::LOGERROR) << "ERROR:"
+#define cWarning() Logger::CDebug(Logger::LOGWARNING)
+#define cError() Logger::CDebug(Logger::LOGERROR)
 
 #endif // CALAMARES_LOGGER_H