RISC-V: Fix accidental embedded -shared regressions.

ld/
	* testsuite/ld-riscv-elf/c-lui.d: Don't use -shared.  Check for _start
	instead of .text.
	* testsuite/ld-riscv-elf/c-lui.s: Add _start label.
	* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Before __global_pointer$
	tests, add call to check_shared_lib_support.

ld/ChangeLog

@@ -1,3 +1,11 @@
+2018-01-08  Jim Wilson  <jimw@sifive.com>
+
+	* testsuite/ld-riscv-elf/c-lui.d: Don't use -shared.  Check for _start
+	instead of .text.
+	* testsuite/ld-riscv-elf/c-lui.s: Add _start label.
+	* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Before __global_pointer$
+	tests, add call to check_shared_lib_support.
+
 2018-01-05  Jim Wilson  <jimw@sifive.com>
 
 	* testsuite/ld-riscv-elf/disas-jalr.d: New.

ld/testsuite/ld-riscv-elf/c-lui.d

@@ -1,7 +1,7 @@
 #name: lui to c.lui relaxation
 #source: c-lui.s
 #as: -march=rv32ic
-#ld: -shared -melf32lriscv
+#ld: -melf32lriscv
 #objdump: -d -M no-aliases,numeric
 
 .*:     file format .*
@@ -9,7 +9,7 @@
 
 Disassembly of section \.text:
 
-.* <.text>:
+.* <_start>:
 .*:	6085                	c.lui	x1,0x1
 .*:	000000b7          	lui	x1,0x0
 .*:	00001037          	lui	x0,0x1

ld/testsuite/ld-riscv-elf/c-lui.s

@@ -1,4 +1,6 @@
 	.text
+	.globl _start
+_start:
 	lui x1, 1
 	lui x1, 0
 	lui x0, 1

ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp

@@ -23,6 +23,11 @@ if [istarget "riscv*-*-*"] {
     run_dump_test "c-lui"
     run_dump_test "disas-jalr"
 
+    # The following tests require shared library support.
+    if ![check_shared_lib_support] {
+	return
+    }
+
     set abis { rv32gc ilp32 elf32lriscv rv64gc lp64 elf64lriscv }
     foreach { arch abi emul } $abis {
 	# This checks whether our linker scripts handle __global_pointer$