[[Bug 21488]] Check 'uname -m' if on Linux and 'uname -p' is unknown

Fixed bug 21488, where on some Linux systems the Makefile is unable to
automatically determine the architecture to build for. This is due to
the Makefile using 'uname -p', which can return 'unknown' in some cases.

Fixed by adding an additional case statement into the Makefile that
checks 'uname -m' if 'unknown' is returned from 'uname -p'.

Author: andrewferguson

Makefile.common

@@ -43,6 +43,10 @@ guess_linux_arch_script := \
 	case `uname -p` in \
 	    x86_64) echo x86_64 ;; \
 	    x86|i*86) echo x86 ;; \
+	    unknown) case `uname -m` in \
+	        x86_64) echo x86_64 ;; \
+                x86|i*86) echo x86 ;; \
+	    esac ;; \
 	esac
 guess_linux_arch := $(shell $(guess_linux_arch_script))