fix: fw-update: make libpldm optional dependency

Only pull in the libpldm dependency if tests are enabled.

The only users of this dependency currently are in the tests.

Change-Id: I17759c536e32c4b15af1f9afd0acde85efe4d3c4
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/meson.build b/meson.build
index 5c6c21c..9214b48 100644
--- a/meson.build
+++ b/meson.build
@@ -64,10 +64,12 @@
 
 subdir('bmc')
 
-libpldm_dep = dependency('libpldm')
+if build_tests.allowed()
+  libpldm_dep = dependency('libpldm')
+endif
 
 common_include = include_directories('.')
 
-if not build_tests.disabled()
+if build_tests.allowed()
   subdir('test')
 endif