Create directory only once when running makefile in parallel - makefile

Question

I'm using make to write a pipeline for biological data analysis. My project directory is:
PROJECT
- DATA
- SAMPLEA
- A1.FASTQ A2.FASTQ
- SAMPLEB
- B1.FASTQ B2.FASTQ
- RESULTS
- SRC
- makefile
My current makefile uses a wildcard to list the directory of all .FASTQ files in the DATA directory. Using pattern rules each .FASTQ file then goes through a series of recipes with the final output file written to the RESULTS directory. Instead, I would like to create a directory for each SAMPLE where the final output file is written:
PROJECT/RESULTS/SAMPLEA/A1.out
PROJECT/RESULTS/SAMPLEA/A2.out
PROJECT/RESULTS/SAMPLEB/B1.out
PROJECT/RESULTS/SAMPLEB/B2.out
I can do this by having the first recipe make the directory, however this throws an error when the second of the FASTQ files from the same SAMPLE also tries to create the directory. A few posts on stack overflow suggest using the -p flag on mkdir to ignore errors, however this apparently causes problems when I run the makefile in parallel using the -j flag. I thought about forcing a shell script at the start of the makefile to run, to check if the results directories are present, and if not then it should create them, but I'd like to try and solve this issue using just make.

Answer 1

Create directory before executing rule.
DATADIR := $(shell cd DATA; find * -type d)
create_results_dir:= $(shell for i in $(DATADIR); \
do test -d DATA/$$i && mkdir -p RESULTS/$$i; \
done)
all:
#echo do something.