boost: Disable build on armv5tel

boost: Disable build on armv5tel

   "g++"   -fvisibility-inlines-hidden -fPIC -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -O2 -pipe -Wall -fexceptions -fPIC -march=armv5te -mfloat-abi=soft -fomit-frame-pointer -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fstack-protector-strong -O3 -fno-strict-aliasing -O2 -pipe -Wall -fexceptions -fPIC -march=armv5te -mfloat-abi=soft -fomit-frame-pointer -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fstack-protector-strong -O3 -fno-strict-aliasing -DBOOST_ALL_NO_LIB=1 -DBOOST_REGEX_DYN_LINK=1 -DNDEBUG  -I"."  -c -o "serial/boost/bin.v2/libs/regex/build/gcc-10.2.0/release/pch-off/visibility-hidden/wide_posix_api.o" "libs/regex/build/../src/wide_posix_api.cpp"

   In file included from ./boost/regex/v5/perl_matcher_non_recursive.hpp:23,
   from ./boost/regex/v5/perl_matcher.hpp:572,
   from ./boost/regex/v5/regex.hpp:45,
   from ./boost/regex.hpp:34,
   from libs/regex/build/../src/wide_posix_api.cpp:25:
   ./boost/regex/v5/mem_block_cache.hpp:91:11: error: 'static_mutex' in namespace 'boost' does not name a type
   91 |    boost::static_mutex mut;
   |           ^~~~~~~~~~~~
   ./boost/regex/v5/mem_block_cache.hpp: In member function 'void* boost::re_detail_500::mem_block_cache::get()':
   ./boost/regex/v5/mem_block_cache.hpp:106:37: error: 'mut' was not declared in this scope; did you mean 'put'?
   106 |       std::lock_guard<std::mutex> g(mut);
   |                                     ^~~
   |                                     put
   ./boost/regex/v5/mem_block_cache.hpp: In member function 'void boost::re_detail_500::mem_block_cache::put(void*)':
   ./boost/regex/v5/mem_block_cache.hpp:120:37: error: 'mut' was not declared in this scope; did you mean 'put'?
   120 |       std::lock_guard<std::mutex> g(mut);
   |                                     ^~~
   |                                     put
   ./boost/regex/v5/mem_block_cache.hpp: In static member function 'static boost::re_detail_500::mem_block_cache& boost::re_detail_500::mem_block_cache::instance()':
   ./boost/regex/v5/mem_block_cache.hpp:137:52: error: 'BOOST_STATIC_MUTEX_INIT' was not declared in this scope; did you mean 'BOOST_STATIC_CONSTANT'?
   137 |       static mem_block_cache block_cache = { 0, 0, BOOST_STATIC_MUTEX_INIT, };
   |                                                    ^~~~~~~~~~~~~~~~~~~~~~~
   |                                                    BOOST_STATIC_CONSTANT
   ./boost/regex/v5/mem_block_cache.hpp:137:77: error: too many initializers for 'boost::re_detail_500::mem_block_cache'
   137 |       static mem_block_cache block_cache = { 0, 0, BOOST_STATIC_MUTEX_INIT, };
   |                                                                             ^
   ...failed updating 2 targets...
   make: *** [boost:102: /usr/src/log/boost_1_76_0] Error 1

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>