runtime: fix aix/ppc64 library initialization

AIX sets the argc and argv parameters in R14 and R15, but
_rt0_ppc64x_lib expects them to be in R3 and R4. Also, call reginit in
_rt0_ppc64x_lib.

These issues were oversights from CL 706395 which went unnoticed because
there if no LUCI aix/ppc64 builder (see #67299).

Change-Id: I93a2798739935fbcead3e6162b4b90db7e740aa5
Reviewed-on: https://go-review.googlesource.com/c/go/+/708255
Reviewed-by: Carlos Amedee <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Junyang Shao <[email protected]>
Reviewed-by: Paul Murphy <[email protected]>

Author: qmuntal

src/runtime/asm_ppc64x.s

@@ -21,6 +21,9 @@ TEXT _rt0_ppc64x_lib(SB),NOSPLIT|NOFRAME,$0
 	MOVD	R4, _rt0_ppc64x_lib_argv<>(SB)
 
 	// Synchronous initialization.
+	MOVD	$runtime·reginit(SB), R12
+	MOVD	R12, CTR
+	BL	(CTR)
 	MOVD	$runtime·libpreinit(SB), R12
 	MOVD	R12, CTR
 	BL	(CTR)

src/runtime/rt0_aix_ppc64.s

@@ -42,4 +42,6 @@ TEXT _main(SB),NOSPLIT,$-8
 	BR (CTR)
 
 TEXT _rt0_ppc64_aix_lib(SB),NOSPLIT,$0
+	MOVD R14, R3 // argc
+	MOVD R15, R4 // argv
 	JMP _rt0_ppc64x_lib(SB)