gnu: Add aws-c-mqtt.

* gnu/packages/c.scm (aws-c-mqtt): New variable.
* gnu/packages/patches/aws-c-mqtt-cmake-prefix.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/local.mk

@@ -876,6 +876,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/aws-c-event-stream-cmake-prefix.patch  \
   %D%/packages/patches/aws-c-http-cmake-prefix.patch		\
   %D%/packages/patches/aws-c-http-disable-networking-tests.patch\
+  %D%/packages/patches/aws-c-mqtt-cmake-prefix.patch		\
   %D%/packages/patches/aws-c-io-cmake-prefix.patch		\
   %D%/packages/patches/aws-c-io-disable-networking-tests.patch	\
   %D%/packages/patches/aws-c-s3-cmake-prefix.patch		\

gnu/packages/c.scm

@@ -834,3 +834,31 @@ authentication.")
 Service (S3) protocol for object storage.")
     (home-page "https://github.com/awslabs/aws-c-s3")
     (license license:asl2.0)))
+
+(define-public aws-c-mqtt
+  (package
+    (name "aws-c-mqtt")
+    (version "0.7.6")
+    (source (origin
+              (method git-fetch)
+              (uri (git-reference
+                    (url (string-append "https://github.com/awslabs/" name))
+                    (commit (string-append "v" version))))
+              (file-name (git-file-name name version))
+              (sha256
+               (base32
+                "0qgblakp9n281z5w1kmmy9sjiz6s44kg487l76w7p43p1dp7s401"))
+              (patches (search-patches "aws-c-mqtt-cmake-prefix.patch"))))
+    (build-system cmake-build-system)
+    (arguments
+     '(#:configure-flags
+       '("-DBUILD_SHARED_LIBS=ON")))
+    (propagated-inputs
+     `(("aws-c-http" ,aws-c-http)
+       ("aws-c-io" ,aws-c-io)))
+    (synopsis "Amazon Web Services MQTT library")
+    (description
+     "This library provides a C99 implementation of the Message Queuing
+Telemetry Transport (MQTT) publish-subscribe messaging protocol.")
+    (home-page "https://github.com/awslabs/aws-c-mqtt")
+    (license license:asl2.0)))

gnu/packages/patches/aws-c-mqtt-cmake-prefix.patch

@@ -0,0 +1,13 @@
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -7,6 +7,10 @@ if (POLICY CMP0069)
+     cmake_policy(SET CMP0069 NEW) # Enable LTO/IPO if available in the compiler, see AwsCFlags
+ endif()
+ 
++if (DEFINED ENV{CMAKE_PREFIX_PATH})
++    set(CMAKE_PREFIX_PATH $ENV{CMAKE_PREFIX_PATH})
++endif()
++
+ if (DEFINED CMAKE_PREFIX_PATH)
+     file(TO_CMAKE_PATH "${CMAKE_PREFIX_PATH}" CMAKE_PREFIX_PATH)
+ endif()