fastddsgen internally calls 'cpp' (the C preprocessor) to resolve
include directives, include guards, etc. See
541129f6e7/src/main/java/com/eprosima/fastdds/fastddsgen.java (L1423)
Make 'cpp' available from the fastddsgen wrapper script. Use the
unwrapped 'cpp', because the wrapped one passes additional parameters,
which make the produced output incompatible with fastddsgen (string out
of bounds exception).
Fixes the error when using IDL files with includes:
```
Processing the file build/foo.idl...
ERROR: Cannot generate the files
begin -3, end 1, length 1
java.lang.StringIndexOutOfBoundsException: begin -3, end 1, length 1
at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4602)
at java.base/java.lang.String.substring(String.java:2705)
at com.eprosima.idl.context.Context.processPreprocessorLine(Context.java:955)
at com.eprosima.idl.parser.grammar.IDLLexer.PREPROC_DIRECTIVE_action(IDLLexer.java:223)
at com.eprosima.idl.parser.grammar.IDLLexer.action(IDLLexer.java:215)
at org.antlr.v4.runtime.atn.LexerCustomAction.execute(LexerCustomAction.java:97)
at org.antlr.v4.runtime.atn.LexerActionExecutor.execute(LexerActionExecutor.java:168)
at org.antlr.v4.runtime.atn.LexerATNSimulator.accept(LexerATNSimulator.java:366)
at org.antlr.v4.runtime.atn.LexerATNSimulator.failOrAccept(LexerATNSimulator.java:299)
at org.antlr.v4.runtime.atn.LexerATNSimulator.execATN(LexerATNSimulator.java:230)
at org.antlr.v4.runtime.atn.LexerATNSimulator.match(LexerATNSimulator.java:114)
at org.antlr.v4.runtime.Lexer.nextToken(Lexer.java:141)
at org.antlr.v4.runtime.BufferedTokenStream.fetch(BufferedTokenStream.java:169)
at org.antlr.v4.runtime.BufferedTokenStream.sync(BufferedTokenStream.java:152)
at org.antlr.v4.runtime.BufferedTokenStream.setup(BufferedTokenStream.java:254)
at org.antlr.v4.runtime.BufferedTokenStream.lazyInit(BufferedTokenStream.java:249)
at org.antlr.v4.runtime.CommonTokenStream.LT(CommonTokenStream.java:92)
at org.antlr.v4.runtime.Parser.enterRule(Parser.java:628)
at com.eprosima.idl.parser.grammar.IDLParser.specification(IDLParser.java:304)
at com.eprosima.fastdds.fastddsgen.parseIDL(fastddsgen.java:809)
at com.eprosima.fastdds.fastddsgen.process(fastddsgen.java:640)
at com.eprosima.fastdds.fastddsgen.execute(fastddsgen.java:458)
at com.eprosima.fastdds.fastddsgen.main(fastddsgen.java:1581)
```
1817b50870