Fixed in branch 1.5.x: print an explanation message with #error if pcap.h is not located. 
See http://bazaar.launchpad.net/~didier-barvaux/rohc/1.5.x/revision/535

The build output now is:

$ make check -C test/non_regression/
make: Entering directory `rohc/rohc-1.5.x/test/non_regression'
make  test_non_regression
make[1]: Entering directory `rohc/rohc-1.5.x/test/non_regression'
  CC     test_non_regression-test_non_regression.o
test_non_regression.c:108:4: error: #error "pcap.h header not found, did you specified --enable-rohc-tests for ./configure ? If yes, check configure output and config.log"
test_non_regression.c:139:32: error: unknown type name 'pcap_dumper_t'
test_non_regression.c:410:32: error: unknown type name 'pcap_dumper_t'
test_non_regression.c: In function 'test_comp_and_decomp':
test_non_regression.c:716:14: error: 'PCAP_ERRBUF_SIZE' undeclared (first use in this function)
test_non_regression.c:716:14: note: each undeclared identifier is reported only once for each function it appears in
test_non_regression.c:717:2: error: unknown type name 'pcap_t'
test_non_regression.c:718:2: error: unknown type name 'pcap_t'
test_non_regression.c:719:2: error: unknown type name 'pcap_dumper_t'
test_non_regression.c:722:21: error: storage size of 'header' isn't known
test_non_regression.c:723:21: error: storage size of 'cmp_header' isn't known
test_non_regression.c:748:2: warning: implicit declaration of function 'pcap_open_offline' [-Wimplicit-function-declaration]
test_non_regression.c:759:2: warning: implicit declaration of function 'pcap_datalink' [-Wimplicit-function-declaration]
test_non_regression.c:760:28: error: 'DLT_EN10MB' undeclared (first use in this function)
test_non_regression.c:761:28: error: 'DLT_LINUX_SLL' undeclared (first use in this function)
test_non_regression.c:762:28: error: 'DLT_RAW' undeclared (first use in this function)
test_non_regression.c:789:3: warning: implicit declaration of function 'pcap_dump_open' [-Wimplicit-function-declaration]
test_non_regression.c:789:10: warning: assignment makes pointer from integer without a cast [enabled by default]
test_non_regression.c:1019:2: warning: implicit declaration of function 'pcap_next' [-Wimplicit-function-declaration]
test_non_regression.c:1034:3: warning: implicit declaration of function 'compress_decompress' [-Wimplicit-function-declaration]
test_non_regression.c:1157:3: warning: implicit declaration of function 'pcap_close' [-Wimplicit-function-declaration]
test_non_regression.c:1162:3: warning: implicit declaration of function 'pcap_dump_close' [-Wimplicit-function-declaration]
test_non_regression.c:723:21: warning: unused variable 'cmp_header' [-Wunused-variable]
test_non_regression.c:722:21: warning: unused variable 'header' [-Wunused-variable]
test_non_regression.c:716:7: warning: unused variable 'errbuf' [-Wunused-variable]
test_non_regression.c: At top level:
test_non_regression.c:1197:12: warning: 'compare_packets' defined but not used [-Wunused-function]
make[1]: *** [test_non_regression-test_non_regression.o] Error 1
make[1]: Leaving directory `rohc/rohc-1.5.x/test/non_regression'
make: *** [check-am] Error 2
make: Leaving directory `rohc/rohc-1.5.x/test/non_regression'