x86: add a Kconfig symbol for when relocations are needed

We only need to build relocations when we are building a 32-bit
relocatable kernel.  Rather than unnecessarily complicating the
Makefiles, make an explicit Kbuild symbol for this.

[ Impact: permits future cleanup ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 039c3f0..5aee453 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1513,6 +1513,11 @@
 	  it has been loaded at and the compile time physical address
 	  (CONFIG_PHYSICAL_START) is ignored.
 
+# Relocation on x86-32 needs some additional build support
+config X86_NEED_RELOCS
+	def_bool y
+	depends on X86_32 && RELOCATABLE
+
 config PHYSICAL_ALIGN
 	hex
 	prompt "Alignment value to which kernel should be aligned" if X86_32