gcc-configure: Enable the use of different symbol versioning

While the gnu style for symbol versioning is the most usual,
--enable-symvers[=style] can be provided several values,
gnu, gnu-versioned-namespace, darwin, darwin-export, and sun,
depending on users needs.

Introduce the SYMVERS_CONF variable to allow the user to
configure the symbol versioning in shared libraries.

(From OE-Core rev: f850931173fc210ed25706fd8fbfe0a310f99dfc)

Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandro@enedino.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/gcc/gcc-configure-common.inc

@@ -17,6 +17,8 @@ GCCTHREADS ?= "posix"
 
 GCCPIE ??= ""
 
+SYMVERS_CONF ?= "--enable-symvers=gnu"
+
 EXTRA_OECONF = "\
     ${@['--enable-clocale=generic', ''][d.getVar('USE_NLS') != 'no']} \
     --with-gnu-ld \
@@ -27,7 +29,7 @@ EXTRA_OECONF = "\
     ${GCCPIE} \
     --enable-c99 \
     --enable-long-long \
-    --enable-symvers=gnu \
+    ${SYMVERS_CONF} \
     --enable-libstdcxx-pch \
     --program-prefix=${TARGET_PREFIX} \
     --without-local-prefix \