[PATCH] configure.ac: fix bashism in configure.ac

[Sam James]

configure scripts need to be runnable with a POSIX-compliant /bin/sh.

On many (but not all!) systems, /bin/sh is provided by Bash, so errors
like this aren't spotted. Notably Debian defaults to /bin/sh provided
by dash which doesn't tolerate such bashisms as '=='.

This retains compatibility with bash.

Fixes configure warnings/errors like:
```
checking if compiler warns about alias for function with incompatible types... yes
/var/tmp/portage/sys-libs/glibc-2.34-r10/work/glibc-2.34/configure: 4209: test: xyes: unexpected operator
```

Signed-off-by: Sam James <sam@gentoo.org>
---
 configure    | 2 +-
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 8e5bee775a..2a3cb49b0b 100755
--- a/configure
+++ b/configure
@@ -4232,7 +4232,7 @@ if test x"$libc_cv_gcc_indirect_function" != xyes; then
   # GCC 8+ emits a warning for alias with incompatible types and it might
   # fail to build ifunc resolvers aliases to either weak or internal
   # symbols.  Disables multiarch build in this case.
-  if test x"$libc_cv_gcc_incompatible_alias" == xyes; then
+  if test x"$libc_cv_gcc_incompatible_alias" = xyes; then
     { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: gcc emits a warning for alias between functions of incompatible types" >&5
 $as_echo "$as_me: WARNING: gcc emits a warning for alias between functions of incompatible types" >&2;}
     if test x"$multi_arch" = xyes; then
diff --git a/configure.ac b/configure.ac
index 87f67d25ec..fa7d3c025b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -767,7 +767,7 @@ if test x"$libc_cv_gcc_indirect_function" != xyes; then
   # GCC 8+ emits a warning for alias with incompatible types and it might
   # fail to build ifunc resolvers aliases to either weak or internal
   # symbols.  Disables multiarch build in this case.
-  if test x"$libc_cv_gcc_incompatible_alias" == xyes; then
+  if test x"$libc_cv_gcc_incompatible_alias" = xyes; then
     AC_MSG_WARN([gcc emits a warning for alias between functions of incompatible types])
     if test x"$multi_arch" = xyes; then
       AC_MSG_ERROR([--enable-multi-arch support requires a gcc with gnu-indirect-function support])
-- 
2.35.1