[PATCH v2 2/6] configure: avoid new clang 11+ warnings

[Daniele Buono]

Clang 11 finds a couple of spots in the code that trigger new warnings:

../qemu-base/hw/usb/dev-uas.c:157:31: error: field 'status' with variable sized 
type 'uas_iu' not at the end of a struct or class is a GNU extension 
[-Werror,-Wgnu-variable-sized-type-not-at-end]
    uas_iu                    status;
                              ^
1 error generated.

The data structure is UASStatus, which must end with a QTAILQ_ENTRY, so
I believe we cannot have uas_iu at the end. Since this is a gnu
extension but CLANG supports it, just add
-Wno-gnu-variable-sized-type-not-at-end
to remove the warning.

../qemu-base/target/s390x/cpu_models.c:985:21: error: cast to smaller integer 
type 'S390Feat' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390Feat feat = (S390Feat) opaque;
                    ^~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1002:21: error: cast to smaller integer 
type 'S390Feat' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390Feat feat = (S390Feat) opaque;
                    ^~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1036:27: error: cast to smaller integer 
type 'S390FeatGroup' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390FeatGroup group = (S390FeatGroup) opaque;
                          ^~~~~~~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1057:27: error: cast to smaller integer 
type 'S390FeatGroup' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390FeatGroup group = (S390FeatGroup) opaque;
                          ^~~~~~~~~~~~~~~~~~~~~~
4 errors generated.

These are void * that get casted to enums, which are (or can be)
smaller than a 64bit pointer.
A code reorg may be better on the long term, but for now will
fix this adding
-Wno-void-pointer-to-enum-cast

Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
---
 configure | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure b/configure
index e6754c1e87..9dc05cfb8a 100755
--- a/configure
+++ b/configure
@@ -2000,6 +2000,8 @@ add_to nowarn_flags -Wno-shift-negative-value
 add_to nowarn_flags -Wno-string-plus-int
 add_to nowarn_flags -Wno-typedef-redefinition
 add_to nowarn_flags -Wno-tautological-type-limit-compare
+add_to nowarn_flags -Wno-gnu-variable-sized-type-not-at-end
+add_to nowarn_flags -Wno-void-pointer-to-enum-cast
 add_to nowarn_flags -Wno-psabi
 
 gcc_flags="$warn_flags $nowarn_flags"
-- 
2.17.1