meson: Allow absence of abi-compliance-check tools

Fixes:

```
Configuring config.h using configuration
Dependency gtest found: YES 1.12.1 (cached)
Dependency gmock found: YES 1.12.1 (cached)
Program abi-dumper found: NO
Program abi-compliance-checker found: NO

../meson.build:85:4: ERROR: Tried to use not-found external program in "command"
```

Tested by issuing `meson setup build && meson compile -C build` both
without and with `abi-dump` and `abi-compliance-checker` installed.
I verified that in the former case we don't fail setup and in the latter
case we check for ABI compliance.

Reported-by: Rashmica Gupta <rashmica@linux.ibm.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ie47c3c0309316cf9d9a46ed26a5a60ee011b6adf
diff --git a/meson.build b/meson.build
index a249774..80d0c93 100644
--- a/meson.build
+++ b/meson.build
@@ -82,28 +82,30 @@
                           abi_compliance_checker.found() and \
                           import('fs').is_file(baseline_dump)
 
-    current_dump = custom_target('abi-dump',
-                             input: libpldm,
-                             output: 'current.dump',
-                             command: [ abi_dumper,
-                                        '-public-headers',
-                                        meson.project_source_root() / 'include',
-                                        '@INPUT@',
-                                        '-o',
-                                        '@OUTPUT@',
-                                        '-lver',
-                                        meson.project_version()])
-    abi_compliance = custom_target('abi-compliance',
-                                   input: [baseline_dump, current_dump],
-                                   output: 'abi-compliance',
-                                   command: [ abi_compliance_checker,
-                                              '-l',
-                                              meson.project_name(),
-                                              '-old',
-                                              '@INPUT0@',
-                                              '-new',
-                                              '@INPUT1@' ],
-                                   build_by_default: test_abi_compliance)
+    if test_abi_compliance
+      current_dump = custom_target('abi-dump',
+                               input: libpldm,
+                               output: 'current.dump',
+                               command: [ abi_dumper,
+                                          '-public-headers',
+                                          meson.project_source_root() / 'include',
+                                          '@INPUT@',
+                                          '-o',
+                                          '@OUTPUT@',
+                                          '-lver',
+                                          meson.project_version()])
+      abi_compliance = custom_target('abi-compliance',
+                                     input: [baseline_dump, current_dump],
+                                     output: 'abi-compliance',
+                                     command: [ abi_compliance_checker,
+                                                '-l',
+                                                meson.project_name(),
+                                                '-old',
+                                                '@INPUT0@',
+                                                '-new',
+                                                '@INPUT1@' ],
+                                                build_by_default: true)
+    endif
   endif
 endif