Add cases for uname() for all known platforms

After what QEMU linux-user says about those.

Not sure what to do for ARM. I used the lowest emulated CPU in QEMU.

src/system/libroot/posix/sys/uname.c

@@ -12,6 +12,7 @@
 #include <unistd.h>
 
 #include <OS.h>
+#include <ByteOrder.h>
 
 #include <errno_private.h>
 #include <system_revision.h>
@@ -58,7 +59,42 @@ uname(struct utsname *info)
 			case B_CPU_x86_64:
 				platform = "x86_64";
 				break;
-			default: //TODO:add others
+			case B_CPU_PPC:
+				platform = "ppc";
+				break;
+			case B_CPU_PPC_64:
+				platform = "ppc64";
+				break;
+			case B_CPU_M68K:
+				platform = "m68k";
+				break;
+			case B_CPU_ARM:
+				/* The minimal ARM version emulated by QEMU
+				 * XXX: use armv6 (raspberry Pi)?
+				 * XXX: should we really use B_HOST_IS_LENDIAN here?
+				 * XXX: use real cpu version as on Linux?
+				 *	cf. http://git.qemu.org/?p=qemu.git;a=blob;f=linux-user/uname.c
+				 */
+#if B_HOST_IS_LENDIAN
+				platform = "armv5tel";
+#else
+				platform = "armv5teb";
+#endif
+				break;
+			case B_CPU_ARM_64:
+				platform = "aarch64";
+				break;
+			case B_CPU_ALPHA:
+				platform = "alpha";
+				break;
+			case B_CPU_MIPS:
+				platform = "mips";
+				break;
+			case B_CPU_SH:
+				platform = "sh4";
+				break;
+			case B_CPU_UNKNOWN:
+			default:
 				platform = "unknown";
 				break;
 		}