[partition] Introduce function for checking various flag-combinations for ESP boot.

src/modules/partition/core/PartUtils.cpp

@@ -340,4 +340,26 @@ isEfiSystem()
     return QDir( "/sys/firmware/efi/efivars" ).exists();
 }
 
+bool
+isEfiBootable( const Partition* candidate )
+{
+    /* If bit 17 is set, old-style Esp flag, it's OK */
+    if ( candidate->activeFlags().testFlag( PartitionTable::FlagEsp ) )
+        return true;
+
+
+    /* Otherwise, if it's a GPT table, Boot (bit 0) is the same as Esp */
+    const PartitionNode* root = candidate;
+    while ( root && !root->isRoot() )
+        root = root->parent();
+
+    // Strange case: no root found, no partition table node?
+    if ( !root )
+        return false;
+
+    const PartitionTable* table = dynamic_cast<const PartitionTable*>( root );
+    return table && ( table->type() == PartitionTable::TableType::gpt ) &&
+        candidate->activeFlags().testFlag( PartitionTable::FlagBoot );
+}
+
 }  // nmamespace PartUtils

src/modules/partition/core/PartUtils.h

@@ -67,6 +67,11 @@ OsproberEntryList runOsprober( PartitionCoreModule* core );
  */
 bool isEfiSystem();
 
+/**
+ * @brief Is the given @p partition bootable in EFI? Depending on
+ * the partition table layout, this may mean different flags.
+ */
+bool isEfiBootable( const Partition* candidate );
 }
 
 #endif // PARTUTILS_H