[glibc] Fix tst-glibc-hwcaps-prepend-cache with custom configure prefix value

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4b4b62191e510230baad7031a5075df6a81e5fa5

commit 4b4b62191e510230baad7031a5075df6a81e5fa5
Author: Romain Geissler <romain.geissler@gmail.com>
Date:   Sun Mar 26 20:00:16 2023 +0000

    Fix tst-glibc-hwcaps-prepend-cache with custom configure prefix value
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 elf/tst-glibc-hwcaps-prepend-cache.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
index 2a44842349..fe074b2802 100644
--- a/elf/tst-glibc-hwcaps-prepend-cache.c
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -44,9 +44,13 @@ do_test (void)
   if (dlopen (SONAME, RTLD_NOW) != NULL)
     FAIL_EXIT1 (SONAME " is already on the search path");
 
-  /* Install the default implementation of libmarkermod1.so.  */
-  xmkdirp ("/etc", 0777);
-  support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+  {
+    /* Install the default implementation of libmarkermod1.so.  */
+    char *conf_path = xasprintf ("%s/ld.so.conf", support_sysconfdir_prefix);
+    xmkdirp (support_sysconfdir_prefix, 0777);
+    support_write_file_string (conf_path, "/glibc-test/lib\n");
+    free (conf_path);
+  }
   xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
   xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
   {