wkhtmltopdf: use qt5.depends_component

allows proper dependency selection for qt5

textproc/wkhtmltopdf/Portfile

@@ -4,6 +4,8 @@ PortSystem          1.0
 PortGroup           github 1.0
 PortGroup           qmake5 1.0
 
+qt5.depends_component qtwebkit qtsvg
+
 github.setup        wkhtmltopdf wkhtmltopdf 0.12.3.2
 checksums           rmd160  67017d05e0455e26e39cf8c6307a3665d0dec853 \
                     sha256  547111465b61b2aa0e1a658209b53682259c038100552ba40dba4e74b12c5d5d
@@ -21,9 +23,6 @@ long_description    \
     rendering engine. These run entirely "headless" and do not require \
     a display or display service.
 
-depends_lib-append  port:qt5-qtwebkit \
-                    port:qt5-qtsvg
-
 patchfiles          patch-src_image_image.pro-use-osx-loader-variable.diff \
                     patch-src_lib_lib.pro-set-install-name.diff \
                     patch-src_pdf_pdf.pro-use-osx-loader-variable.diff