[gdb/testsuite] Fix compare-sections.exp with -fPIE/-pie

When running gdb.base/compare-sections.exp with target board -fPIE/-pie, we
get:
...
FAIL: gdb.base/compare-sections.exp: after run to main: compare-sections -r
...

The test expects the read-only sections to have the same contents as in the
file:
...
    # Assume startup code doesn't change read-only sections.
    compare_sections "-r"
...
but that's not the case for PIE executables.

Fix this by allowing mismatched read-only sections for PIE executables.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2019-08-16  Tom de Vries  <tdevries@suse.de>

	* gdb.base/compare-sections.exp ("after run to main"): Allow
	mismatched read-only sections for PIE executables.

1 files changed, 9 insertions, 2 deletions

diff --git a/gdb/testsuite/gdb.base/compare-sections.exp b/gdb/testsuite/gdb.base/compare-sections.exp
index 7dbae5b..75667ee 100644
--- a/gdb/testsuite/gdb.base/compare-sections.exp
+++ b/gdb/testsuite/gdb.base/compare-sections.exp
@@ -21,6 +21,8 @@ if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug}]} {
     return -1
 }
 
+set is_pie [exec_is_pie $binfile]
+
 # Run the compare-sections command along with any options as specified
 # by OPTIONS, and check that no mismatch is found.
 proc compare_sections { {options ""} } {
@@ -87,8 +89,13 @@ with_test_prefix "after run to main" {
     gdb_test "compare-sections" \
 	"MIS-MATCHED.*warning.*One or more sections.*does not match.*loaded file"
 
-    # Assume startup code doesn't change read-only sections.
-    compare_sections "-r"
+    if { $is_pie == 1 } {
+	gdb_test "compare-sections -r" \
+	    "MIS-MATCHED.*warning.*One or more sections.*does not match.*loaded file"
+    } else {
+	# Assume startup code doesn't change read-only sections.
+	compare_sections "-r"
+    }
 }
 
 # Now test that "compare-sections -r" works as expected.  Look for an