[JITLink][PowerPC] Pre-commit test for D155925. NFC.

Author: Kai Luo

llvm/test/ExecutionEngine/JITLink/ppc64/Inputs/external_weak.s

@@ -0,0 +1,13 @@
+	.text
+	.abiversion 2
+	.weak	foo
+	.p2align	4
+	.type	foo,@function
+foo:
+.Lfunc_begin0:
+	li 3, 1
+	blr
+	.long	0
+	.quad	0
+.Lfunc_end0:
+	.size	foo, .Lfunc_end0-.Lfunc_begin0

llvm/test/ExecutionEngine/JITLink/ppc64/Inputs/external_weak_main.s

@@ -0,0 +1,37 @@
+	.text
+	.abiversion 2
+	.weak	foo
+	.p2align	4
+	.type	foo,@function
+foo:
+.Lfunc_begin0:
+	li 3, 0
+	blr
+	.long	0
+	.quad	0
+.Lfunc_end0:
+	.size	foo, .Lfunc_end0-.Lfunc_begin0
+
+	.globl	main
+	.p2align	4
+	.type	main,@function
+main:
+.Lfunc_begin1:
+.Lfunc_gep1:
+	addis 2, 12, .TOC.-.Lfunc_gep1@ha
+	addi 2, 2, .TOC.-.Lfunc_gep1@l
+.Lfunc_lep1:
+	.localentry	main, .Lfunc_lep1-.Lfunc_gep1
+	mflr 0
+	stdu 1, -32(1)
+	std 0, 48(1)
+	bl foo
+	nop
+	addi 1, 1, 32
+	ld 0, 16(1)
+	mtlr 0
+	blr
+	.long	0
+	.quad	0
+.Lfunc_end1:
+	.size	main, .Lfunc_end1-.Lfunc_begin1

llvm/test/ExecutionEngine/JITLink/ppc64/external_weak.s

@@ -0,0 +1,17 @@
+# REQUIRES: asserts
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=powerpc64le-unknown-linux-gnu -filetype=obj -o \
+# RUN:   %t/external_weak.o %S/Inputs/external_weak.s
+# RUN: llvm-mc -triple=powerpc64le-unknown-linux-gnu -filetype=obj -o \
+# RUN:   %t/external_weak_main.o %S/Inputs/external_weak_main.s
+# RUN: llvm-jitlink -noexec -debug-only=jitlink %t/external_weak.o \
+# RUN:   %t/external_weak_main.o 2>&1 | FileCheck %s
+# CHECK: Created ELFLinkGraphBuilder for "{{.*}}external_weak_main.o"
+# CHECK: Creating defined graph symbol for ELF symbol "foo"
+# CHECK: External symbols:
+# CHECK:   {{.*}} linkage: weak, scope: default, dead  -   foo
+# CHECK: section .text:
+# CHECK:   {{.*}} kind = CallBranchDelta, target = foo
+# `foo` is weak in both relocatable files. `foo` is resolved to the one
+# defined in `%t/external_weak.o`. So calling `foo` in `%t/external_weak_main.o`
+# is expected to be an external function call.