[PATCH 17/18] trace-cmd: Fix the logic behind SWIG_DEFINED in the Makefile

["Vladislav Valtchev (VMware)" <vladislav.valtchev@gmail.com>]

At least on Ubuntu, the $(shell ...) command used in the master Makefile to test
for the existence of the 'swig' command does not work in the negative case.
That causes the build to report ugly errors in case 'swig' is not installed on
the system.
This one-line patch, fixes the problem by using the POSIX 'comamnd -v {CMD}'
in $(shell ...) to detect the presence of the swig and restores this way the
fake report_noswig target.

Signed-off-by: Vladislav Valtchev (VMware) <vladislav.valtchev@gmail.com>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index c5da7c8..0a2a78d 100644
--- a/Makefile
+++ b/Makefile
@@ -102,7 +102,7 @@ ifndef VERBOSE
   VERBOSE = 0
 endif
 
-SWIG_DEFINED := $(shell if swig -help &> /dev/null; then echo 1; else echo 0; fi)
+SWIG_DEFINED := $(shell if command -v swig; then echo 1; else echo 0; fi)
 ifeq ($(SWIG_DEFINED), 0)
 BUILD_PYTHON := report_noswig
 NO_PYTHON = 1
@@ -115,7 +115,7 @@ PYTHON_GUI	:= ctracecmd.so ctracecmdgui.so
 PYTHON_VERS ?= python
 
 # Can build python?
-ifeq ($(shell sh -c "pkg-config --cflags $(PYTHON_VERS) > /dev/null 2>&1 && which swig && echo y"), y)
+ifeq ($(shell sh -c "pkg-config --cflags $(PYTHON_VERS) > /dev/null 2>&1 && echo y"), y)
 	PYTHON_PLUGINS := plugin_python.so
 	BUILD_PYTHON := $(PYTHON) $(PYTHON_PLUGINS)
 	BUILD_PYTHON_WORKS := 1
-- 
2.14.1