fix(ghidra): handle PIE base address when opening the r2pipe

If we are trying to decompile a running binary which is a PIE, we need
to make sure to pass the appropriate base address to radare2 to be used
when loading a new binary.

Furthermore set io.cache to fix relocations in disassembly and avoid a
warning from the r2pipe.

pwndbg/radare2.py

@@ -1,3 +1,5 @@
+import pwndbg.elf
+
 radare2 = {}
 
 
@@ -6,7 +8,10 @@ def r2pipe(filename):
     if r2:
         return r2
     import r2pipe
-    r2 = r2pipe.open(filename)
+    flags = ['-e', 'io.cache=true']
+    if pwndbg.elf.get_elf_info(filename).is_pie and pwndbg.elf.exe():
+        flags.extend(['-B', hex(pwndbg.elf.exe().address)])
+    r2 = r2pipe.open(filename, flags=flags)
     radare2[filename] = r2
     r2.cmd("aaaa")
     return r2