Reduce duplicate NOASM and PSEUDO definitions

The initial value of NOASM is nearly the same in all cases and the
initial value of PSEUDO is the same in all cases so reduce duplication
(and hopefully, future merge conflicts) by machine independent defaults.

Also document the PSEUDO variable.

Reviewed by:	jhb, kib
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D7820

lib/libc/aarch64/sys/Makefile.inc

@@ -11,13 +11,5 @@ MDASM=	cerror.S \
 	vfork.S
 
 # Don't generate default code for these syscalls:
-NOASM=	break.o \
-	exit.o \
-	getlogin.o \
-	sbrk.o \
-	sstk.o \
-	vfork.o \
-	yield.o
-
-PSEUDO= _exit.o \
-	_getlogin.o
+NOASM+=	sbrk.o \
+	vfork.o

lib/libc/amd64/sys/Makefile.inc

@@ -8,6 +8,4 @@ MDASM=	vfork.S brk.S cerror.S exect.S getcontext.S \
 	sbrk.S setlogin.S sigreturn.S
 
 # Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o vfork.o yield.o
-
-PSEUDO=	_getlogin.o _exit.o
+NOASM+=	vfork.o

lib/libc/arm/sys/Makefile.inc

@@ -5,6 +5,4 @@ SRCS+=	__vdso_gettc.c
 MDASM= Ovfork.S brk.S cerror.S sbrk.S shmat.S sigreturn.S syscall.S
 
 # Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o vfork.o yield.o
-
-PSEUDO= _exit.o _getlogin.o
+NOASM+=	vfork.o

lib/libc/i386/sys/Makefile.inc

@@ -10,10 +10,7 @@ SRCS+=	i386_get_fsbase.c i386_get_gsbase.c i386_get_ioperm.c i386_get_ldt.c \
 MDASM=	Ovfork.S brk.S cerror.S exect.S getcontext.S \
 	sbrk.S setlogin.S sigreturn.S syscall.S
 
-# Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o vfork.o yield.o
-
-PSEUDO=	_getlogin.o _exit.o
+NOASM+=	vfork.o
 
 MAN+=	i386_get_ioperm.2 i386_get_ldt.2 i386_vm86.2
 MAN+=	i386_set_watch.3

lib/libc/mips/sys/Makefile.inc

@@ -6,6 +6,4 @@ MDASM=  Ovfork.S brk.S cerror.S exect.S \
 	sbrk.S syscall.S
 
 # Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o vfork.o yield.o
-
-PSEUDO= _exit.o _getlogin.o
+NOASM+=	vfork.o

lib/libc/powerpc/sys/Makefile.inc

@@ -1,8 +1,3 @@
 # $FreeBSD$
 
 MDASM+=	brk.S cerror.S exect.S sbrk.S setlogin.S
-
-# Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o yield.o
-
-PSEUDO=	_getlogin.o _exit.o

lib/libc/powerpc64/sys/Makefile.inc

@@ -1,8 +1,3 @@
 # $FreeBSD$
 
 MDASM+=	brk.S cerror.S exect.S sbrk.S setlogin.S
-
-# Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o yield.o
-
-PSEUDO=	_getlogin.o _exit.o

lib/libc/riscv/sys/Makefile.inc

@@ -10,13 +10,4 @@ MDASM=	cerror.S \
 	vfork.S
 
 # Don't generate default code for these syscalls:
-NOASM=	break.o \
-	exit.o \
-	getlogin.o \
-	sbrk.o \
-	sstk.o \
-	vfork.o \
-	yield.o
-
-PSEUDO= _exit.o \
-	_getlogin.o
+NOASM+=	vfork.o

lib/libc/sparc64/sys/Makefile.inc

@@ -13,8 +13,3 @@ SRCS+=	__sparc_sigtramp_setup.c \
 CFLAGS+= -I${LIBC_SRCTOP}/sparc64/fpu
 
 MDASM+=	brk.S cerror.S exect.S sbrk.S setlogin.S sigaction1.S
-
-# Don't generate default code for these syscalls:
-NOASM=	break.o exit.o getlogin.o sstk.o yield.o
-
-PSEUDO=	_getlogin.o _exit.o

lib/libc/sys/Makefile.inc

@@ -12,7 +12,18 @@
 #
 # MDASM names override the default syscall names in MIASM.
 # NOASM will prevent the default syscall code from being generated.
+# PSEUDO generates _<sys>() and __sys_<sys>() symbols, but not <sys>().
 #
+# While historically machine dependent, all archictures have the following
+# declerations in common:
+#
+NOASM=	break.o \
+	exit.o \
+	getlogin.o \
+	sstk.o \
+	yield.o
+PSEUDO=	_exit.o \
+	_getlogin.o
 .sinclude "${LIBC_SRCTOP}/${LIBC_ARCH}/sys/Makefile.inc"
 
 SRCS+= clock_gettime.c gettimeofday.c __vdso_gettimeofday.c