Remove references to bundled mbedtls library to use the one from inputs.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e27d21..f0eb1a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,13 +85,6 @@ endif()
 
 set(USE_STATIC_MBEDTLS_LIBRARY ON)
 set(USE_SHARED_MBEDTLS_LIBRARY OFF)
-add_subdirectory("lib/mbedtls" EXCLUDE_FROM_ALL)
-
-# Compile the mbedtls library as a static with position independent code,
-# because we need it for both a shared and static library
-set_property(TARGET mbedtls PROPERTY POSITION_INDEPENDENT_CODE ON)
-set_property(TARGET mbedcrypto PROPERTY POSITION_INDEPENDENT_CODE ON)
-set_property(TARGET mbedx509 PROPERTY POSITION_INDEPENDENT_CODE ON)
 
 add_subdirectory(src)
 
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<tr><td><span title='2020-11-18 22:31:32 +0100'>2020-11-18</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=0ae9bbe4f5f89e6f597bdb1f6df646fc5f504876'>services: SDDM: Wait for elogind before starting.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-04-19 09:06:20 +0300'>2020-04-19</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=fafe2343c29bcb02fcee79558fbd8ae2ba2c1214'>services: sddm: Have sddm provision xorg-server.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-03-01 14:13:27 +0100'>2020-03-01</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=50be0da7bfd5c108697679effeb2a893d2f37598'>services: set-xorg-configuration: handle slim and sddm</a><span class='msg-avail'>...</span></td><td>Jakub Kądziołka</td></tr>
<tr><td><span title='2020-02-16 09:25:00 +0200'>2020-02-16</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=3c6aca4232d1a3638ec962bc7afe9121626c43ec'>doc: Fix typo.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2019-10-21 18:16:16 +0200'>2019-10-21</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=cfe8d8063b5d79fc91eb757c2020244e239b77b3'>services: sddm: Add description.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-21 18:16:16 +0200'>2019-10-21</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=8cf3e167c15a0dba3166cbeee46d41f26cbf75f1'>services: sddm: Deprecate 'sddm-service' procedure.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-21 18:16:16 +0200'>2019-10-21</span></td><td><a href='/guix/commit/gnu/services/sddm.scm?id=5ac5f2c1298cac811a544e2db193ba5d69d9fce6'>services: sddm: Add default configuration.</a><span class='msg-avail'>...</span></td><td>Brendan Tildesley</td></tr>