package/uhd: fix build with riscV

From: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>

UHD with riscV CPU fails to build with error like:
/xxx/output-1/build/uhd-3.15.0.0/host/lib/deps/rpclib/include/rpc/msgpack/pack.hpp:190:2: error: #error msgpack-c supports only big endian and little endian
  190 | #error msgpack-c supports only big endian and little endian
      |  ^~~~~

msgpack, required by MPMD, support many architecture but not riscV, and,
consequently is unable to determine the endianess.

This patch add a depends on !(BR2_RISCV_64 || BR2_RISCV_32) to disable MPMD
for riscV target.
Since E300 and E320 needs MPMD, the select is replaced by depends on

Fixes:
- http://autobuild.buildroot.net/results/b501a8bf90f2eb10c3f98f26a52539392d320088/
- http://autobuild.buildroot.net/results/f7ae898c6ecdfa568eb97f7cae6447e97ce306a0/

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
---
 package/uhd/Config.in | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Gwenhael, All,

On 2020-10-30 16:31 +0100, Gwenhael Goavec-Merou spake thusly:
> From: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
> 
> UHD with riscV CPU fails to build with error like:
> /xxx/output-1/build/uhd-3.15.0.0/host/lib/deps/rpclib/include/rpc/msgpack/pack.hpp:190:2: error: #error msgpack-c supports only big endian and little endian
>   190 | #error msgpack-c supports only big endian and little endian
>       |  ^~~~~
> 
> msgpack, required by MPMD, support many architecture but not riscV, and,
> consequently is unable to determine the endianess.

The issue is two folds:
 1. uhd bundles (or re-implements?) its own copy of msgpack-c;
 2. the bundled msgpack-c borked its detection of the endianness.

So, I think a better solution would be to actually fix the endian
detection [0]. Indeed, a CPU is either big or little endian [1], so
failing to detect actually detect that is pretty serious...

[0] uhd-3.15.0.0/host/lib/deps/rpclib/include/rpc/msgpack/predef/other/endian.h

[1] Yeah, back in the good old days, we had mixed endian CPUs that were
word-swapped, but those really no longer exist, and are definitely not a
target for Buildroot.

Regards,
Yann E. MORIN.

> This patch add a depends on !(BR2_RISCV_64 || BR2_RISCV_32) to disable MPMD
> for riscV target.
> Since E300 and E320 needs MPMD, the select is replaced by depends on
> 
> Fixes:
> - http://autobuild.buildroot.net/results/b501a8bf90f2eb10c3f98f26a52539392d320088/
> - http://autobuild.buildroot.net/results/f7ae898c6ecdfa568eb97f7cae6447e97ce306a0/
> 
> Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
> ---
>  package/uhd/Config.in | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/package/uhd/Config.in b/package/uhd/Config.in
> index 32cb4cf89d..cf4f470629 100644
> --- a/package/uhd/Config.in
> +++ b/package/uhd/Config.in
> @@ -45,13 +45,13 @@ config BR2_PACKAGE_UHD_B200
>  
>  config BR2_PACKAGE_UHD_E300
>  	bool "E300 support"
> -	select BR2_PACKAGE_UHD_MPMD
> +	depends on BR2_PACKAGE_UHD_MPMD
>  	help
>  	  enable E300 support
>  
>  config BR2_PACKAGE_UHD_E320
>  	bool "E320 support"
> -	select BR2_PACKAGE_UHD_MPMD
> +	depends on BR2_PACKAGE_UHD_MPMD
>  	help
>  	  enable E320 support
>  
> @@ -62,6 +62,7 @@ config BR2_PACKAGE_UHD_EXAMPLES
>  
>  config BR2_PACKAGE_UHD_MPMD
>  	bool "MPMD support"
> +	depends on !(BR2_RISCV_64 || BR2_RISCV_32)
>  	help
>  	  enable MPMD support
>  
> -- 
> 2.20.1
> 
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