Provide a small shim binary that tries to find the actual tool and exec() it.
Prefers the llvm version but falls back to the classic version if necessary.

--- cctools-895/misc/llvm-shim.c.orig	2017-12-26 14:10:13.019362000 +0100
+++ cctools-895/misc/llvm-shim.c	2017-12-26 14:12:25.590790515 +0100
@@ -0,0 +1,68 @@
+#include <unistd.h>
+#include <string.h>
+#include "stuff/allocate.h"
+#include "stuff/execute.h"
+#include "stuff/errors.h"
+
+/* used by system_fatal */
+char *progname = NULL;
+
+int main(int argc, char **argv)
+{
+	char *prog2, *prog2_path;
+
+	progname = argv[0];
+	prog2 = strrchr(argv[0], '/');
+	if (prog2 != NULL)
+		progname = prog2 + 1;
+
+	/* looks like we've been called with CTARGET in our name - let's try to
+	 * get rid of it */
+	prog2 = strstr(progname, "-apple-darwin");
+	if (prog2 != NULL) {
+		/* x86_64-apple-darwin16-nm
+		 *       ^ p */
+		prog2 += strlen("-apple-darwin");
+
+		/*                    ^ */
+		prog2 = strchr(prog2, '-');
+		/*                      ^ */
+		if (prog2 != NULL) {
+		        /*               ^ */
+			progname = prog2+1;
+		}
+	}
+
+	/* try ./llvm-<tool> */
+	prog2 = makestr("llvm-", progname, NULL);
+	prog2_path = cmd_with_prefix(prog2);
+	if(access(prog2_path, F_OK) == -1) {
+		/* try to find llvm-<tool> in prefix (eg llvm-nm) */
+		try_hard_to_find_llvm_tool_in_prefix(&prog2_path, "bin", prog2);
+		if (access(prog2_path, F_OK) == -1) {
+			/* try to find ./<tool> in prefix (eg dsymutil) */
+			try_hard_to_find_llvm_tool_in_prefix(&prog2_path, "bin", progname);
+			if (access(prog2_path, F_OK) == -1) {
+				/* try ./<tool>-classic (eg nm-classic) */
+				prog2 = makestr(progname, "-classic", NULL);
+				prog2_path = cmd_with_prefix(prog2);
+				if(access(prog2_path, F_OK) == -1) {
+					/* bail out */
+					system_fatal("can't find: %s", progname);
+				}
+			}
+		}
+	}
+
+	/* give the new program its full path in argv[0], just as if it had
+	 * been called directly */
+	argv[0] = prog2_path;
+
+	/* will not normally return */
+	execvp(prog2_path, argv);
+
+	/* will exit(1) */
+	system_fatal("can't exec: %s", progname);
+
+	return 1;
+}
--- cctools-895/misc/Makefile.orig	2017-12-25 13:29:59.700143547 +0100
+++ cctools-895/misc/Makefile	2017-12-25 13:33:18.817740929 +0100
@@ -39,7 +39,7 @@
 LOCBINDIR = /usr/local/bin
 LOCLIBDIR = /usr/local/lib
 
-CFILES1 = libtool.c
+CFILES1 = libtool.c llvm-shim.c
 CFILES2 = lipo.c size.c strings.c nm.c checksyms.c inout.c \
 	 indr.c strip.c segedit.c cmpdylib.c \
 	 pagestuff.c redo_prebinding.c seg_addr_table.c \
@@ -53,6 +53,7 @@
 	indr.NEW strip.NEW nmedit.NEW segedit.NEW cmpdylib.NEW \
 	pagestuff.NEW redo_prebinding.NEW seg_addr_table.NEW check_dylib.NEW \
 	seg_hack.NEW install_name_tool.NEW codesign_allocate.NEW \
+	llvm-shim.NEW \
 	ctf_insert.NEW bitcode_strip.NEW
 
 all:	$(PROGS) lib_ofiles
@@ -246,6 +247,14 @@
 		$(OFILE_DIR)/bitcode_strip.private.o
 	$(DSYMUTIL) $(SYMROOT)/bitcode_strip.NEW
 
+llvm-shim.NEW: llvm-shim.o $(OBJROOT)/.created.dir.stamp $(SYMROOT)/.created.dir.stamp
+	$(CC) $(RC_CFLAGS) -nostdlib -r \
+		-o $(OBJROOT)/llvm-shim.private.o \
+		$(OFILE_DIR)/llvm-shim.o $(LIBSTUFF)
+	$(CC) $(RC_CFLAGS) $(SDK) -o $(SYMROOT)/llvm-shim.NEW \
+		$(OFILE_DIR)/llvm-shim.private.o
+	$(DSYMUTIL) $(SYMROOT)/llvm-shim.NEW
+
 
 clean: shlib_clean
 	-rm -f \
@@ -271,6 +280,7 @@
 	$(SYMROOT)/redo_prebinding.NEW \
 	$(SYMROOT)/libredo_prebinding.a \
 	$(SYMROOT)/cmpdylib.NEW \
+	$(SYMROOT)/llvm-shim.NEW \
 	$(SYMROOT)/bitcode_strip.NEW
 
 shlib_clean:
@@ -319,6 +329,7 @@
 	$(OFILE_DIR)/cmpdylib.private.o \
 	$(OFILE_DIR)/nmedit.private.o \
 	$(OFILE_DIR)/strip.private.o \
+	$(OFILE_DIR)/llvm-shim.private.o \
 	$(OFILE_DIR)/bitcode_strip.private.o
 	-rm -f make.out
 	-rm -r -f *dSYM
@@ -360,6 +371,8 @@
 			  $(DSTROOT)$(USRBINDIR)/ctf_insert
 	install -m 555 $(SYMROOT)/bitcode_strip.NEW \
 			  $(DSTROOT)$(USRBINDIR)/bitcode_strip
+	install -m 555 $(SYMROOT)/llvm-shim.NEW \
+			  $(DSTROOT)$(USRBINDIR)/llvm-shim
 	$(MKDIRS) $(DSTROOT)$(LOCBINDIR)
 	install -m 555 $(SYMROOT)/checksyms.NEW \
 			  $(DSTROOT)$(LOCBINDIR)/checksyms