Keep chroot indication only in prepare()

It's not actually needed by other methods.

rootfs.py

@@ -110,8 +110,7 @@ def main():
 
     system_c = SysC(arch=args.arch, preserve_tmp=args.preserve,
             tmpdir=args.tmpdir, chroot=args.chroot)
-    system_b = SysB(arch=args.arch, preserve_tmp=args.preserve,
-            chroot=args.chroot)
+    system_b = SysB(arch=args.arch, preserve_tmp=args.preserve)
     system_a = SysA(arch=args.arch, preserve_tmp=args.preserve,
                     tmpdir=args.tmpdir, chroot=args.chroot,
                     sysb_dir=system_b.sys_dir, sysc_tmp=system_c.tmp_dir)

sysa.py

@@ -33,14 +33,13 @@ class SysA(SysGeneral):
         self.cache_dir = os.path.join(self.sys_dir, 'distfiles')
         self.sysb_dir = sysb_dir
         self.sysc_tmp = sysc_tmp
-        self.chroot = chroot
 
-        self.prepare()
+        self.prepare(chroot)
 
         if not chroot:
             self.make_initramfs()
 
-    def prepare(self):
+    def prepare(self, chroot):
         """
         Prepare directory structure for System A.
         We create an empty tmpfs, unpack stage0-posix.
@@ -54,7 +53,7 @@ class SysA(SysGeneral):
         # sysb must be added to sysa as it is another initramfs stage
         self.sysb()
 
-        if self.chroot:
+        if chroot:
             self.sysc()
 
     def sysa(self):

sysb.py

@@ -12,10 +12,9 @@ class SysB(SysGeneral):
     """
     Class responsible for preparing sources for System B.
     """
-    def __init__(self, arch, preserve_tmp, chroot):
+    def __init__(self, arch, preserve_tmp):
         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, 'sysb')

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