How to set if else within a flag for a makefile

[mar11]

Do i have any possibility to set if/else within a flag which contains a coupile of libraries. COnsider this example:

FLAG -L$(LIBRAY1_DIR) -L$(LIBRAY2_DIR) -llibrary1 - library2

What i want do to do is for some compilation i want to include the second library - library2 and for other compilation i do not want to include it.

I have done as the following(i am a beginner with Make). But it did not work at all.

FLAG -L$(LIBRAY1_DIR) -L$(LIBRAY2_DIR) \
- library1 \
ifdef$(VARIABLE) \
-llibrary1 \
endif

How can i automazie this action?

[donbock]

Which version make are you using?

How do you want to tell make which option to take?
(for instance, command line argument, different make targets, something else)

[mar11]

I have the version 3.81

If there are more than one possibility to choose specific compiler-flag as i have described then i will appreciate to get some of suggestions.

[donbock]

Sorry I wasn't clear. There are many different make programs out there. Which one are you using?

Version number 3.81 is consistent with gnu make.

[mar11]

Sorry, I still do not understand you what do you actually want to know!!

I think my question was clear enough as i described above. please can you read it again..

any suggestions...

[newb16]

did you try to search for 'gnu make conditional' in google?
Does something like this work?

ifdef FLAG
  libs2 = -library2
else
# or leave it empty?
  libs2 = 
endif
 
FLAG -L$(LIBRAY1_DIR) -L$(LIBRAY2_DIR) -library1 $(libs2)
 

[donbock]

There are many different make programs in use today. How they support conditional instructions varies. If I don't know which make program you are using then I might give you the wrong advice.

[mar11]

@donebock

let us make the life more easy and tell me please how can i check which make Program do i use...