Don't run C tests in ld testsuite unless we have a C compiler

Removing the [isnative] check requires that we test for a C compiler.

	* testsuite/ld-elf/elf.exp: Check that $CC exists before C tests.
	* testsuite/ld-pie/pie.exp: Likewise.
	* testsuite/ld-plugin/lto.exp: Likewise.

ld/ChangeLog

@@ -1,3 +1,9 @@
+2017-01-03  Alan Modra  <amodra@gmail.com>
+
+	* testsuite/ld-elf/elf.exp: Check that $CC exists before C tests.
+	* testsuite/ld-pie/pie.exp: Likewise.
+	* testsuite/ld-plugin/lto.exp: Likewise.
+
 2017-01-02  Alan Modra  <amodra@gmail.com>
 
 	* Makefile.am (bootstrap): Delete rule.

ld/testsuite/ld-elf/elf.exp

@@ -221,6 +221,11 @@ if { [istarget *-*-*linux*]
 
 set LDFLAGS $old_ldflags
 
+# Check to see if the C compiler works
+if { [which $CC] == 0 } {
+    return
+}
+
 if [check_gc_sections_available] {
     run_cc_link_tests {
 	{"PR ld/13195" "-Wl,--gc-sections" ""

ld/testsuite/ld-pie/pie.exp

@@ -25,6 +25,11 @@ if { ![istarget *-*-linux*]
     return
 }
 
+# Check to see if the C compiler works
+if { [which $CC] == 0 } {
+    return
+}
+
 # Check if -pie is supported or not.
 send_log "$CC -fpie -pie $srcdir/$subdir/pie.c -o tmpdir/pie"
 catch "exec $CC -fpie -pie $srcdir/$subdir/pie.c -o tmpdir/pie" exec_output

ld/testsuite/ld-plugin/lto.exp

@@ -18,6 +18,11 @@
 # Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
 # MA 02110-1301, USA.
 
+# Check to see if the C compiler works
+if { [which $CC] == 0 } {
+    return
+}
+
 # These tests require plugin and LTO.
 if { ![check_plugin_api_available]
      || ![check_lto_available] } {