Run __init__() even in sysimage builds

This change makes the LinearAlgebra initialization code run during the
sysimage build, similar to how it would run when using LinearAlgebra at
top-level in a normal package.

In this configuration, we can't rely on the serializer to isolate
side-effects for us, so we have to manually ensure that any mutations
that we perform here are not accidentally persisted to run-time.

Author: topolarity

src/LinearAlgebra.jl

@@ -841,6 +841,8 @@ function lbt_openblas_onload_callback()
         end
         BLAS.lbt_set_num_threads(nthreads)
     end
+
+    return nothing
 end
 
 function __init__()
@@ -849,4 +851,7 @@ function __init__()
     libblastrampoline_jll.add_dependency!(OpenBLAS_jll, libopenblas, lbt_openblas_onload_callback)
 end
 
+# Register eagerly, so that LinearAlgebra is available for sysimage builds (incl. `--trim`)
+libblastrampoline_jll.add_dependency!(OpenBLAS_jll, libopenblas, lbt_openblas_onload_callback)
+
 end # module LinearAlgebra