Many build systems (well, ubuntu's one for sure)
add -Wl,-Bsymbolic-functions to LDFLAGS. After that,
libpsx doesn't work as it can't override psx_load_syscalls.

I propose this small hack as a fix:

diff --git a/libcap/Makefile b/libcap/Makefile
index f5dde3e..b23a925 100644
--- a/libcap/Makefile
+++ b/libcap/Makefile
@@ -21,6 +21,10 @@ PSXMAGICOBJ=psx_magic.o
 # Always build libcap sources this way:
 CFLAGS += -fPIC
 
+# Many build systems add -Bsymbolic-functions - remove
+CMA = ,
+LDFLAGS := $(filter-out -Wl$(CMA)-Bsymbolic-functions,$(LDFLAGS))
+
 # The linker magic needed to build a dynamic library as independently
 # executable
 MAGIC=-Wl,-e,__so_start