Update approach to obtain the head git hash

.travis.yml

@@ -128,8 +128,6 @@ after_success:
       && echo https://px4-travis.s3.amazonaws.com/archives/Firmware/$TRAVIS_BRANCH/$TRAVIS_BUILD_ID/Firmware.zip
       ;
     fi
-  - git log -n 1 --pretty=format:"%H"
-  - git rev-parse HEAD
 
 deploy:
   provider: releases

cmake/common/px4_base.cmake

@@ -700,7 +700,7 @@ function(px4_create_git_hash_header)
 		REQUIRED HEADER 
 		ARGN ${ARGN})
 	execute_process(
-		COMMAND git log -n 1 --pretty=format:"%H"
+		COMMAND git rev-parse HEAD
 		OUTPUT_VARIABLE git_desc
 		OUTPUT_STRIP_TRAILING_WHITESPACE
 		WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}

cmake/templates/build_git_version.h.in

@@ -1,4 +1,4 @@
 /* Auto Magically Generated file */
 /* Do not edit! */
-#define PX4_GIT_VERSION_STR  @git_desc@
+#define PX4_GIT_VERSION_STR  "@git_desc@"
 #define PX4_GIT_VERSION_BINARY 0x@git_desc_short@