supposing that u are making a %.o file from a %.pc file
-> search for the rule written for making %.o from %.pc
there may be a intermediate step like %.pc -> %.c and then %.c -> %.o
while searching for %.pc inside your makefile, u will find the variable name used for proc compiler, if it is PROC, then search for "include", this is to conform if the Makefile is including any other file, which is altering the value of PROC
->Find how is the PROC value created, it is also possible that, it is created using ORACLE_HOME or ORACLE_BIN(if exist).You can do it by searching for PROC inside Makefile and other make related files

->check your environment and other files(.login , .profile etc depending upon the shell you are using ) responsible for environment
->setenv or set would list out the env variable, check what is the value of ORACLE_HOME or other ORACLE related env variables
setenv | grep -i ORACLE
or you can see manually

->if the env variable is holding the wrong value or if there is a invalid path in the file.Then you should change that

->from your statements I personally feel that the problem is with the env, not in Makefile (Some time you may get errors in Makefile, due to usage of older version of Make )

Rakesh