libcontainer: merge common syscall implementations

There are essentially two possible implementations for Setuid/Setgid on
Linux, either using SYS_SETUID32/SYS_SETGID32 or SYS_SETUID/SYS_SETGID,
depending on the architecture (see golang/go#1435 for why Setuid/Setgid
aren currently implemented for Linux neither in syscall nor in
golang.org/x/sys/unix).

Reduce duplication by merging the currently implemented variants and
adjusting the build tags accordingly.

Signed-off-by: Tobias Klauser <[email protected]>

Author: tklauser

libcontainer/system/syscall_linux_386.go renamed to libcontainer/system/syscall_linux_32.go

@@ -1,4 +1,5 @@
-// +build linux,386
+// +build linux
+// +build 386 arm
 
 package system
 

libcontainer/system/syscall_linux_64.go

@@ -1,4 +1,5 @@
-// +build linux,arm64 linux,amd64 linux,ppc linux,ppc64 linux,ppc64le linux,s390x
+// +build linux
+// +build arm64 amd64 mips mipsle mips64 mips64le ppc ppc64 ppc64le s390x
 
 package system