meson: adjust nlohmann-json dependency

Simplify the dependency logic and align wrap file directives with
other repositories.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I61209bcd25995ef447c790e59ad717c1192acbc2
diff --git a/bmc/meson.build b/bmc/meson.build
index 3d9e5e6..40ca2b3 100644
--- a/bmc/meson.build
+++ b/bmc/meson.build
@@ -1,7 +1,7 @@
 bmc_inc = include_directories('.')
 
 common_pre = declare_dependency(
-  dependencies: [json_dep],
+  dependencies: [nlohmann_json_dep],
   include_directories: [root_inc, bmc_inc])
 
 common_lib = static_library(
diff --git a/meson.build b/meson.build
index b28fc5e..83a1f4f 100644
--- a/meson.build
+++ b/meson.build
@@ -128,14 +128,7 @@
   link_with: sys_lib)
 
 blobs_dep = dependency('phosphor-ipmi-blobs')
-
-cpp = meson.get_compiler('cpp')
-
-if cpp.has_header('nlohmann/json.hpp')
-    json_dep = declare_dependency()
-else
-    json_dep = dependency('nlohmann_json')
-endif
+nlohmann_json_dep = dependency('nlohmann_json', include_type: 'system')
 
 if not get_option('tests').disabled()
   gtest = dependency('gtest', main: true, disabler: true, required: false)
diff --git a/subprojects/nlohmann_json.wrap b/subprojects/nlohmann_json.wrap
index 477e844..3745380 100644
--- a/subprojects/nlohmann_json.wrap
+++ b/subprojects/nlohmann_json.wrap
@@ -1,6 +1,6 @@
 [wrap-git]
-url = https://github.com/nlohmann/json
 revision = HEAD
+url = https://github.com/nlohmann/json.git
 
 [provide]
 nlohmann_json = nlohmann_json_dep