[flang][OMP] change malloc.h to stdlib.h in collapse_test.inc (NFC)

[kkwli]

malloc.h is in .../usr/include/malloc/malloc.h on MacOS. Using stdlib.h works for Mac and other platforms.

[luporl]

LGTM.

I also get a 'malloc.h' file not found error on macOS, without this change.

[ceseo]

LGTM. This fixes most of the build failures I've seen in SPEC CPU 2017 on macOS.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder openmp-offload-libc-amdgpu-runtime running on omp-vega20-1 while building openmp at step 7 "Add check check-offload".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/11630

Here is the relevant piece of the build log for the reference

Step 7 (Add check check-offload) failure: test (failure)
******************** TEST 'libomptarget :: amdgcn-amd-amdhsa :: offloading/pgo1.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/clang -fopenmp    -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src  -nogpulib -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib  -fopenmp-targets=amdgcn-amd-amdhsa /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c -o /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload/test/amdgcn-amd-amdhsa/offloading/Output/pgo1.c.tmp -Xoffload-linker -lc -Xoffload-linker -lm /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib/libomptarget.devicertl.a -fprofile-instr-generate      -Xclang "-fprofile-instrument=clang"
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/clang -fopenmp -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -nogpulib -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -Wl,-rpath,/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib -fopenmp-targets=amdgcn-amd-amdhsa /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c -o /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload/test/amdgcn-amd-amdhsa/offloading/Output/pgo1.c.tmp -Xoffload-linker -lc -Xoffload-linker -lm /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./lib/libomptarget.devicertl.a -fprofile-instr-generate -Xclang -fprofile-instrument=clang
# RUN: at line 3
/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload/test/amdgcn-amd-amdhsa/offloading/Output/pgo1.c.tmp 2>&1 | /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/FileCheck /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c      --check-prefix="CLANG-PGO"
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/offload/test/amdgcn-amd-amdhsa/offloading/Output/pgo1.c.tmp
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/FileCheck /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c --check-prefix=CLANG-PGO
# .---command stderr------------
# | /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c:32:20: error: CLANG-PGO-NEXT: expected string not found in input
# | // CLANG-PGO-NEXT: [ 0 11 20 ]
# |                    ^
# | <stdin>:3:28: note: scanning from here
# | ======== Counters =========
# |                            ^
# | <stdin>:4:1: note: possible intended match here
# | [ 0 14 20 ]
# | ^
# | 
# | Input file: <stdin>
# | Check file: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/offloading/pgo1.c
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            1: ======= GPU Profile ======= 
# |            2: Target: amdgcn-amd-amdhsa 
# |            3: ======== Counters ========= 
# | next:32'0                                X error: no match found
# |            4: [ 0 14 20 ] 
# | next:32'0     ~~~~~~~~~~~~
# | next:32'1     ?            possible intended match
# |            5: [ 10 ] 
# | next:32'0     ~~~~~~~
# |            6: [ 20 ] 
# | next:32'0     ~~~~~~~
# |            7: ========== Data =========== 
# | next:32'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |            8: { 9515997471539760012 4749112401 0xffffffffffffffd8 0x0 0x0 0x0 3 0 0 } 
# | next:32'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |            9: { 3666282617048535130 24 0xffffffffffffffb0 0x0 0x0 0x0 1 0 0 } 
# | next:32'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |            .
# |            .
# |            .
...