Make building the bfloat16 functions conditional on option BUILD_HALF (#2590)

* make building the bfloat16 BLAS functions conditional on BUILD_HALF

* pass the BUILD_HALF option to gensymbol

* Pass BUILD_HALF as a compiler define for dynamic_arch builds

cmake/kernel.cmake

@@ -113,6 +113,7 @@ macro(SetDefaultL1)
   set(ZSUMKERNEL zsum.S)
   set(QSUMKERNEL sum.S)
   set(XSUMKERNEL zsum.S)
+if (BUILD_HALF)
   set(SHAMINKERNEL ../arm/amin.c)
   set(SHAMAXKERNEL ../arm/amax.c)
   set(SHMAXKERNEL ../arm/max.c)
@@ -131,6 +132,7 @@ macro(SetDefaultL1)
   set(SHNRM2KERNEL ../arm/nrm2.c)
   set(SHSUMKERNEL ../arm/sum.c)
   set(SHSWAPKERNEL ../arm/swap.c)
+endif ()
 endmacro ()
 
 macro(SetDefaultL2)
@@ -179,10 +181,11 @@ macro(SetDefaultL2)
   set(XHEMV_L_KERNEL ../generic/zhemv_k.c)
   set(XHEMV_V_KERNEL ../generic/zhemv_k.c)
   set(XHEMV_M_KERNEL ../generic/zhemv_k.c)
+if (BUILD_HALF)
   set(SHGEMVNKERNEL ../arm/gemv_n.c)
   set(SHGEMVTKERNEL ../arm/gemv_t.c)
   set(SHGERKERNEL ../generic/ger.c)
-
+endif ()
 endmacro ()
 
 macro(SetDefaultL3)
@@ -190,6 +193,7 @@ macro(SetDefaultL3)
   set(DGEADD_KERNEL ../generic/geadd.c)
   set(CGEADD_KERNEL ../generic/zgeadd.c)
   set(ZGEADD_KERNEL ../generic/zgeadd.c)
+if (BUILD_HALF)
   set(SHGEADD_KERNEL ../generic/geadd.c)
   set(SHGEMMKERNEL ../generic/gemmkernel_2x2.c)
   set(SHGEMM_BETA  ../generic/gemm_beta.c)
@@ -201,6 +205,6 @@ macro(SetDefaultL3)
   set(SHGEMMITCOPYOBJ shgemm_itcopy.o)
   set(SHGEMMONCOPYOBJ shgemm_oncopy.o)
   set(SHGEMMOTCOPYOBJ shgemm_otcopy.o)
-
+endif ()
 
 endmacro ()