Keep chroot indication only in prepare()

It's not actually needed by other methods.

sysc.py

@@ -24,7 +24,6 @@ class SysC(SysGeneral):
         self.git_dir = os.path.dirname(os.path.join(__file__))
         self.arch = arch
         self.preserve_tmp = preserve_tmp
-        self.chroot = chroot
 
         self.sys_dir = os.path.join(self.git_dir, 'sysc')
         self.cache_dir = os.path.join(self.sys_dir, 'distfiles')
@@ -34,7 +33,7 @@ class SysC(SysGeneral):
             self.tmp_dir = os.path.join(tmpdir, 'sysc')
             os.mkdir(self.tmp_dir)
 
-        self.prepare()
+        self.prepare(chroot)
 
     def __del__(self):
         if not self.preserve_tmp:
@@ -44,7 +43,7 @@ class SysC(SysGeneral):
 
         super().__del__()
 
-    def prepare(self):
+    def prepare(self, chroot):
         """
         Prepare directory structure for System C.
         """
@@ -52,7 +51,7 @@ class SysC(SysGeneral):
 
         rootfs_dir = None
 
-        if not self.chroot:
+        if not chroot:
             # Create + mount a disk for QEMU to use
             disk_path = os.path.join(self.tmp_dir, 'disk.img')
             self.dev_name = create_disk(disk_path, "msdos", "ext4", '8G')
@@ -70,7 +69,7 @@ class SysC(SysGeneral):
         copytree(self.sys_dir, rootfs_dir, ignore=shutil.ignore_patterns("tmp"))
 
         # Unmount tmp/mnt if it exists
-        if not self.chroot:
+        if not chroot:
             umount(rootfs_dir)
 
     # pylint: disable=line-too-long,too-many-statements