Improve type stability of rpaths(RPath(oh::ELFHandle))

Previously, we'd get `Vector{Any}`, but we actually want
`Vector{AbstractString}`.

src/ELF/ELFDynamicLink.jl

@@ -89,7 +89,7 @@ Stores the RPath entries from an ELF object
 """
 struct ELFRPath{H <: ELFHandle} <: RPath{H}
     section_ref::SectionRef{H}
-    rpath::Vector
+    rpath::Vector{<:AbstractString}
 end
 
 """
@@ -106,13 +106,18 @@ function RPath(oh::ELFHandle)
     des = ELFDynEntries(oh, [DT_RPATH, DT_RUNPATH])
 
     # Lookup each and every one of those strings, split them out into paths
-    colon_paths = [strtab_lookup(d) for d in des]
-    paths = vcat([split(p, ":") for p in colon_paths]...)
+    colon_paths = String[strtab_lookup(d) for d in des]
+    paths = AbstractString[]
+    for colon_path in colon_paths
+        for component in split(colon_path, ':')
+            push!(paths, component)
+        end
+    end
 
     # Return our RPath object
     return ELFRPath(dyn_section, paths)
 end
 
 Section(rpath::ELFRPath) = rpath.section_ref
 handle(rpath::ELFRPath) = handle(Section(rpath))
-rpaths(rpath::ELFRPath) = rpath.rpath
+rpaths(rpath::ELFRPath) = rpath.rpath